WO2011026905A1

WO2011026905A1 - Blade device for silk-screen printing on a substrate or a print support and relative printing method

Info

Publication number: WO2011026905A1
Application number: PCT/EP2010/062882
Authority: WO
Inventors: Tommaso Vercesi; Andrea Baccini; Giorgio Cellere; Luigi De Santi; Marco Galiazzo; Gianfranco Pasqualin
Original assignee: Applied Materials, Inc.
Priority date: 2009-09-03
Filing date: 2010-09-02
Publication date: 2011-03-10
Also published as: TW201129479A

Abstract

Blade device for the silk-screen printing of one or more print tracks on substrates, or print supports (150), by means of a print material (11) able to be deposited on a net (12) comprising a sheet (14) that defines, in its inactive condition, a first lying plane (P1). The blade is rotatable so as to be able to selectively vary the inclination thereof with respect to said first lying plane (P1), to define one or more desired angulations with respect to a portion of the upper surface of the sheet (14) on which the print material is progressively delivered.

Description

"BLADE DEVICE FOR SILK-SCREEN PRINTING ON A SUBSTRATE OR A PRINT SUPPORT AND RELATIVE PRINTING METHOD"

FIELD OF THE INVENTION

The present invention concerns a blade device for the silk-screen printing of one or more print tracks on a substrate, or print support, for example for the silk- screen printing of conductive tracks on plate elements for electronics, or similar elements, such as a wafer, a substrate or thin sheet, with a silicon base, in order to make photovoltaic cells. However, it cannot be excluded that, as a print support, another specific print support may be provided, typical of other fields in which a printing operation is provided.

BACKGROUND OF THE INVENTION

It is known that a technique to make conductive tracks on silicon-based wafers, in particular but not only for photovoltaic cells, is silk-screen printing, using suitable print materials, such as for example conductive pastes or inks, and a suitable silk-screen net, normally consisting of a warp and weft mesh, having on the lower side an emulsion is disposed, appropriately incised according to the desired development of the tracks to be made.

Silk-screen printing provides to use one or more blades or brushes, also called squeeges, by means of which, with a determinate and constant pressure, the print material is spread on the silk-screen net.

Normally, the printing blade acts on the net according to a desired fixed angular orientation with respect to the theoretical horizontal plane on which the net lies. The orientation of the blade can also influence the quantity and speed with which the print material is printed and hence on the final quality of the printing process.

The net is normally supported by a peripheral frame. Moreover, the material which makes up the net typically has a determinate flexibility.

The pressure of the printing blade, in particular in proximity with the external support frame, can determine a deflection of the net, even considerable, with respect to the hypothetic horizontal lying plane of the net.

As a result of the different deflection deriving therefrom, together with the fact that the printing blade has a fixed angular orientation with respect to the hypothetical lying plane of the net, the actual inclination of the surface of the net varies dynamically in the course of the printing pass of the blade.

Therefore, the actual angle created between the blade and the net also varies, also considerably in proximity to the peripheral frame.

Consequently, the same delivery conditions cannot always be guaranteed with which the print material is printed through the incisions of the net, which negatively affects the quality and reproducibility of the print.

Furthermore, variations in height may occur relating to the presence or absence of emulsion.

Moreover, with regard to the warp and weft, the net in any case has differences in depth between the longitudinal and transverse developments, due to the local overlapping of warp and weft, and therefore does not guarantee a constant angle of incidence of the blade on the net.

In conclusion, the mechanical constraint that angularly fixes the blade with respect to the theoretical plane on which the net lies does not guarantee, due to the phenomena illustrated above, constant delivery conditions of the print material through the net. This can limit the repeatability and quality of the print.

It is also known that, when the print material is drawn by the blade on the net, normally only a small percentage of the material actually passes through the net, and thus forms the tracks on the printing substrate. However, most of the print material is only moved by the blade from one side of the net to the other.

When several substrates have to be printed, it is therefore convenient to use a recovery or flooding blade which, moving in coordination with or independently of the printing blade, recovers the excess print material in order to make it available for the blade for printing the next substrate. The flooding blade is typically mounted on a dedicated support and is moved and controlled by a combination of both dedicated actuators and also the same actuators that move and control the printing blade. This creates a greater complexity of the mechanical structure and of the control of the various movement elements.

Furthermore, due to a non-optimum distribution, partial drying out and/or anomalies in the functioning of the feed circuit or the movement of the blades, the print material tends to be distributed in excess in some zones, or to form accumulations which lead to a poorer quality of the print on the wafer below. It is therefore necessary to periodically clean the nets, usually mechanically by means of scraping devices, using a spatula, knife or scraper proper, which act by eliminating the accumulations of print material.

The provision of the scraper devices, however, is not simple to do, since the space available in the printing heads is normally limited. In addition to this, making the additional scraper devices in any case increases the bulk of the printing head and the number of movement, drive and control mechanisms to be provided.

Purpose of the present invention is to achieve a blade device for silk-screen printing and to perfect a relative printing method, which guarantee that the angular orientation of the blade is maintained with respect to the actual surface of the net in the course of the printing action, even in the event of deflections of the net during the printing operation or variations in depth due to the warp and weft structure of the net.

Another purpose of the present invention is to achieve a blade device for silk- screen printing which allows to recover the print material and/or to clean the net simply, rapidly, automatically and economically.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with the above purpose, a blade device according to the present invention can be used for the silk-screen printing of one or more print tracks on substrates, or print supports, by means of a print material able to be deposited on a net comprising a sheet that defines, in its inactive condition, a first lying plane. The blade device of the present invention comprises:

- a printing extremity able to act with pressure on an upper surface of said sheet to determine the printing of the print material through the net;

- a frame able to support said printing extremity and lying on a second lying plane which defines a determinate first angle with respect to said first plane; - translation means to make linearly advance said blade device on the net with an alternate linear movement, to carry out the desired printing operation.

According to the present invention the blade device comprises movement means able to determine the selective rotation of said blade to selectively vary the inclination thereof with respect to said first lying plane, to define one or more desired angulations with respect to a portion of the upper surface of the sheet on which the print material is progressively delivered.

The activation of said movement means is autonomous with respect to the activation of aid translation means.

The movement means is configurable to maintain constant a second angle between the second lying plane of the frame and said portion of the upper surface of the sheet, advantageously in the course of the printing operation itself, which portion is inclined with respect to said first angle following the deformation of the sheet due to the action of the printing extremity.

The blade device further comprises sensor means suitable for detecting desired data relating to the variation in the reciprocal angular position between the blade device and the deformed surface of the sheet.

The blade device of the present invention comprises a system controller being provided, able to automatically control and command the rotation of said blade according to signals received from said sensor means relating to the reciprocal angular position of said blade and said portion of the surface of the sheet.

In some forms of embodiment, the movement means comprises a cylindrical actuator.

In further forms of embodiment, the movement means comprises motor means rotatably constrained, by means of an articulation member, to said blade device.

In some embodiments, said motor means are suitable for driving linear actuation means rotatably constrained, by means of said articulation member, to said frame, in order to rotate the blade device.

Another aspect of the present invention concerns a method for the silk-screen printing of one or more print tracks on print supports by means of a print material deposited on a net formed by a sheet that defines, in its inactive condition, a first lying plane

The method of the present invention comprises a step of acting with pressure on an upper surface of said sheet to determine the printing of the print material through the net by means of a blade device having a print extremity that is supported lying on a second lying plane which defines a determinate first angle with respect to said first plane.

The method of the present invention further comprises a step of linearly advancing the blade device on the net with an alternate linear movement, to carry out the desired printing operation.

According to the present invention, the method further comprises the step of rotating said blade device to selectively vary the inclination thereof with respect to said first lying plane, to define desired angulations with respect to a portion of the upper surface of the sheet on which the print material is progressively delivered.

The step of rotating is performed to maintain constant a second angle between the second lying plane of the frame and said portion of the upper surface of the sheet, which portion is inclined with respect to said first angle following the deformation of the sheet due to the action of the printing extremity.

According to the present invention, the rotation of the blade device is automatically controlled and commanded, autonomously with respect to the step of linearly advancing the blade device on the net, according to signals received relating to the reciprocal angular position of said blade and said portion of the surface of the sheet.

According to an advantageous variant of the method, the selective inclination of the blade is effected dynamically during printing.

The blade device according to the present invention therefore has the possibility of modifying its angle of inclination with respect to the theoretical lying plane of the net.

This allows to compensate the angular variations between the lying plane of the blade and the theoretical lying plane of the net due to the different deflection of the net in the course of printing, and thus to maintain the angle constant between the plane of the blade and the actual inclined surface of the net.

In this way we obtain constant delivery conditions of the print material through the net and therefore repeatability and quality of the print are guaranteed. The variable inclination of the blade according to the present invention can be determined independently of the further operativeness of the printing head, allowing:

- to regulate the angle of inclination of the blade at start of printing according to the type of net and/or the type of print material and/or the type of print desired;

- to regulate the angle of inclination of the blade even during the printing operation in order to compensate the different flexing of the surface of the net and/or different height of the net between warp and weft of the net and/or the variations in height relating to the presence or absence of the emulsion, and/or the greater or lesser resistance to printing of the print material, due to the density of the print material itself;

- a local acceleration of the travel of the blade, with respect to the alternative printing movement typical of the blade block mounted on the printing head, appropriately varying the angle of incidence of the blade and, on the contrary, keeping constant the overall speed of advance of the blade block.

Advantageously, the possibility of accelerating or decelerating the blade device locally, varying the inclination thereof, allows for example to have a slower printing speed in correspondence with the edges of the wafers to be printed, allowing a better control of the printing in this peripheral region, whereas a greater speed is possible in the central region of the wafer to be printed.

With the inclination of the blade device according to the invention it is also possible to vary the pressure that is applied on the net, and to apply different operating delivery conditions during the course of the printing step.

In some embodiments, with the blade device according to the invention it is possible to rotate the print extremity so as to change from a position control mode, for example in correspondence with the periphery of the net where the blade is adjusted in position with respect to the net and substrate, to a pressure control mode, during printing operation.

Moreover, the invention allows to vary the angle of the blade to change the printing quality, for example inclining the blade further forward in correspondence with determinate regions of the net, to have a bigger quantity of print material that is pressed and printed onto the substrate below.

Another advantage of the solution according to the present invention is that it provides data, for example relating to the inclination of the blade according to the properties of the net and/or the print material used, that can possibly be memorized by the system controller, in order to control and regulate, according to said data, the subsequent operating steps and/or subsequent operating cycles. According to some further forms of embodiments of the present invention, the blade device also comprises at least a print material recovery or flooding and/or cleaning member, integrated therewith, to recover the print material and/or to clean the excess print material from the net.

In a form of embodiment, when the blade and the recovery or flooding and/or cleaning member return to the starting position, they provide the recovered printing material for a subsequent printing operation.

According to the invention, the blade device has at least one operating condition for printing, in which said print extremity is able to act on the net, and at least one operating condition for recovery and/or cleaning, in which said recovery and/or cleaning member is able to act on the net so as to recover the print material, or to clean the net.

In this way, a blade device is achieved that integrates both the function of printing and also the function of recovery and/or cleaning. The one or more recovery and/or cleaning members provided, since they are integrated with the blade which acts above the net, do not cause any problems of bulk nor are they constrained to the limited spaces that normally exist around the printing head.

Advantageously, the present invention therefore provides a single actuator and two distinct commands to pass between the two operating conditions as above, of which a first command determines the operating condition for printing and a second command determines the operating condition for recovering the material and cleaning the net. The two commands are advantageously driven by means of a single actuator that determines the desired movement to pass from one operating condition to the other.

The blade device according to the present invention therefore simplifies the construction of the system for recovering the print material or for cleaning the net, and considerably facilitates the mechanical management thereof.

It is clear that, according to a variant, at least the operating condition for recovery and/or cleaning may include a plurality of different positions of the blade; for example there may be two angular positions symmetrical with respect to a central position of the blade in which printing is performed, depending on the direction in which the blade has to act on the net.

According to a variant, the blade device is selectively movable, advantageously automatically, to pass from the operating condition for printing to the operating condition for recovery and/or cleaning, and vice versa.

A specific variant embodiment provides that said recovery and/or cleaning member is disposed in correspondence with said print extremity.

According to another variant, the print extremity and the recovery and/or cleaning member are reciprocally movable, advantageously automatically, to pass from the operating condition for printing to the operating condition for recovery and/or cleaning, and vice versa. For example, it may be that the recovery and/or cleaning member is mobile telescopically with respect to the print extremity, having a retracted position inside the bulk of the print extremity when inactive, and a position protruding from the bulk of the print extremity when active.

According to another variant, the blade comprises at least two recovery and/or cleaning members disposed on opposite sides with respect to the print extremity. Advantageously, the two recovery and/or cleaning members can in turn be reciprocally movable, for example rotatable, so as to vary the incidence with which they contact the net.

According to one form of embodiment, the blade comprises two recovery members disposed on opposite sides with respect to the print extremity.

According to another form of embodiment, the blade comprises one member to recover the print material on one side with respect to the print extremity and one cleaning member on the opposite side with respect to the print extremity. This has the advantage that it integrates three complementary functions, that is: printing, recovering the material and cleaning the net, all in a single blade.

According to one form of embodiment of said variant, the operating condition for recovery and/or cleaning may include, or in any case may be set in, at least two different positions angularly staggered on opposite sides with respect to the operating condition for printing, for example used depending on the direction of advance of the blade along the net. In these two positions, a corresponding recovery and/or cleaning member of said two recovery and/or cleaning members is alternately active.

Another variant provides that said two recovery and/or cleaning members are disposed in substantial correspondence with said print extremity, on opposite sides with respect to said print extremity, and are conformed so as to define a window through which said print extremity protrudes.

According to this variant, in said operating condition for printing, the window faces toward the net so that the print extremity can act on the net, whereas said recovery and/or cleaning members are separated from the net.

According to another variant, in said operating condition for recovery and/or cleaning, the window is distanced from the net so that the print extremity is separated from the net and one of the recovery and/or cleaning members can act on the net.

According to a variant, the recovery and/or cleaning member comprises at least a blade, scraper, scraping spatula or knife, able to achieve the recovery of the material or the mechanical cleaning of the net.

According to a specific variant, the recovery and/or cleaning members comprise two blades, scrapers, scraping spatulas or knives, each of which is formed by a first segment that extends transversely on opposite sides with respect to the print extremity, and by a second segment that extends transversely from said first segment, toward said print extremity, so as to partly surround the print extremity and define the window.

Alternatively, or in combination, the recovery and/or cleaning member comprises at least tape-like means able to clean the net, such as a paper with an adhesive layer, or a fabric.

In accordance with one form of embodiment, the blade comprises movement means able to determine the passage from the operating condition for printing to the condition for recovery and/or cleaning, and vice versa.

The movement means are common to the print extremity and to the recovery and/or cleaning members and are configurable with two distinct commands, for example sent from a system controller, to pass from one operating condition to the other.

According to another variant, the blade comprises, traditionally, a frame to support the print extremity. According to a variant solution, the recovery and/or cleaning member is mounted on the frame, in proximity with the print extremity.

Consequently, the print extremity and the recovery and/or cleaning member are positioned and supported by means of the common support frame. This renders advantageous the sharing of the movement by means of a single drive mean or actuator and two distinct commands. The support frame in turn is linearly translatable, at least parallel to the net, to carry out printing or the operation of recovery and/or cleaning.

According to a variant solution, the movement means are able to determine the selective rotation of the blade between the operating condition for printing and the operating condition for recovery and/or cleaning.

Another variant is that the movement means are able to determine the reciprocal movement of said print extremity and said recovery and/or cleaning member to pass alternatively between the operating condition for printing and the operating condition for recovery and/or cleaning.

According to a variant of the invention, the blade is made to translate along and above the net, by means of translation means, usually for the purposes of printing.

According to a variant solution, the translation means determine both the linear translation of the blade to perform the printing, and also the linear translation of the blade set in the operating condition for recovery and/or cleaning, in order to recover the material or for cleaning.

This is advantageous since it allows to minimize the drive mechanisms for printing and recovery or cleaning, unlike in the state of the art where the components that effect the printing and those which effect the recovery each have their own drive mechanism.

Advantageously, the movement means that determine the passage from the printing condition to the recovery and/or cleaning condition, and vice versa, are autonomous with respect to the translation means which determine the movement of linear translation thereof.

Another variant provides that the blade comprises or is associated with a system controller, able to control and command the passage from the operating condition for printing to the operating condition for recovery and/or cleaning, for example according to data directly or indirectly correlated to the degree of dirtiness of the net caused by the excess print material.

Another advantage of the solution according to the present invention is that it supplies at least some of said data which can possibly be memorized by the system controller, in order to control and regulate, according to said data, the subsequent operating steps and/or cycles.

Another aspect of the present invention concerns a printing head for the silk- screen printing of one or more print tracks on substrates, or print supports, comprising a blade device according to the present invention as described above.BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

- Figure 1 is a schematic isometric view of a processing system that can be used with a blade according to the present invention;

- Figure 2 is a schematic plan view of the system depicted in Figure 1 ;

- Figure 3 is a schematic view of a blade device according to the present invention, in a first operating condition

- Figure 4 is a schematic view of the blade device in Figure 3, in a second operating condition;

- Figure 5 is a schematic view of the blade device in Figure 3, in a third operating condition

- Figure 6 is a schematic view of the blade device in Figure 3, in a fourth operating condition;

- Figure 7 shows one form of embodiment of a blade device according to the present invention.

- Figure 8 is a schematic view of a blade device according to a further embodiment of present invention, in an operating condition for printing;

- Figure 9 is a schematic view of the blade device of Figure 8, in an operating condition for recovery and/or cleaning;

- Figure 10 is another schematic view the blade device of Figure 8, in an operating condition for recovery and/or cleaning;

- Figure 1 1 shows one form of embodiment of the blade device of Figure 8; - Figure 12 is a perspective view of a part of the blade device in Figure 11;

- Figure 13 is a lateral view of the part of the blade device in Figure 1 1.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF

EMBODIMENT

With reference to the attached drawings, Figures 1 - 7 disclose a blade device 10 according to the present invention which is used for the silk-screen printing in a suitable printing head 102 of a substrate processing system, or system, 100 for printing a screen print material 1 1 , in this case conductive paste, on a substrate 150 by means of a silk-screen net 12, in order to reproduce desired conductive tracks on substrates, or print supports, 150, in this case plate elements for electronics or suchlike, located below the net 12, for example silicon-based wafers to make photovoltaic cells.

Figure 1 is a schematic isometric view of the system 100, used with the blade device 10 according to one embodiment of the present invention. In one embodiment, the system 100 generally includes two incoming conveyors 1 1 1, an actuator assembly 140, a plurality of processing nests 131, a plurality of printing heads 102, two outgoing conveyors 1 12, and a system controller 101. The incoming conveyors 1 11 are configured in a parallel processing configuration so that each can receive unprocessed substrates 150 from an input device, such as an input conveyor 1 13, and transfer each unprocessed substrate 150 to a processing nest 131 coupled to the actuator assembly 140. Additionally, the outgoing conveyors 1 12 are configured in parallel so that each can receive a processed substrate 150 from a processing nest 131 and transfer each processed substrate 150 to a substrate removal device, such as an exit conveyor 1 14. In one embodiment, each exit conveyor 1 14 is adapted to transport processed substrates 150 through an oven 199 to cure material deposited on the substrate 150 via the printing heads 102.

In one embodiment, substrates 150 are microcrystalline silicon substrates used for processing solar cells thereon. In another embodiment, substrates 150 are green tape ceramic substrates or the like.

In one embodiment of the present invention, the system 100 is a screen printing processing system and the printing heads 102 include screen printing components, which are configured to screen print a patterned layer of material on a substrate 150. In another embodiment, the system 100 is a processing system that includes material removal components in the printing head 102, such as a laser for ablating or etching one or more regions of a substrate 150. In other embodiments, the system 100 may comprise other substrate processing modules requiring precise movement and positioning of the substrates for processing. Figure 2 is a schematic plan view of the system 100 depicted in Figure 1. Figures 1 and 2 illustrate the system 100 having two processing nests 131 (in positions "1" and "3") each positioned to both transfer a processed substrate 150 to the outgoing conveyor 1 12 and receive an unprocessed substrate 150 from the incoming conveyor 1 1 1. Thus, in the system 100, the substrate motion generally follows the path "A" shown in Figures 1 and 2. In this configuration, the other two processing nests 131 (in positions "2" and "4") are each positioned under a printing head 102 so that a process (e.g., screen printing) can be performed on the unprocessed substrates 150 situated on the respective processing nests 131. Such a parallel processing configuration allows increased processing capacity with a minimized processing system footprint. Although, the system 100 is depicted having two printing heads 102 and four processing nests 131, the system 100 may comprise additional printing heads 102 and/or processing nests 131 without departing from the scope of the present invention.

In one embodiment, the incoming conveyor 1 1 1 and outgoing conveyor 1 12 include at least one belt 116 to support and transport the substrates 150 to a desired position within the system 100 by use of an actuator (not shown) that is in communication with the system controller 101. While Figures 1 and 2 generally illustrate a two belt style substrate transferring system, other types of transferring mechanisms may be used to perform the same substrate transferring and positioning functions without varying from the basic scope of the invention.

In one embodiment, the system 100 also includes an inspection system 200, which is adapted to locate and inspect the substrates 150 before and after processing has been performed. The inspection system 200 may include one or more cameras 120 that are positioned to inspect a substrate 150 positioned in the loading/unloading positions "1" and "3," as shown in Figures 1 and 2. The inspection system 200 generally includes at least one camera 120 (e.g., CCD camera) and other electronic components that are able to locate, inspect, and communicate the results to the system controller 101. In one embodiment, the inspection system 200 locates the position of certain features of an incoming substrate 150 and communicates the inspection results to the system controller 101 for analysis of the orientation and position of the substrate 150 to assist in the precise positioning of the substrate 150 under a printing head 102 prior to processing the substrate 150. In one embodiment, the inspection system 200 inspects the substrates 150 so that damaged or mis-processed substrates can be removed from the production line. In one embodiment, the processing nests 131 may each contain a lamp, or other similar optical radiation device, to illuminate the substrate 150 positioned thereon so that it can be more easily inspected by the inspection system 200.

The system controller 101 facilitates the control and automation of the overall system 100 and may include a central processing unit (CPU) (not shown), memory (not shown), and support circuits (or I/O) (not shown). The CPU may be one of any form of computer processors that are used in industrial settings for controlling various chamber processes and hardware (e.g., conveyors, detectors, motors, fluid delivery hardware, etc.) and monitor the system and chamber processes (e.g., substrate position, process time, detector signal, etc.). The memory is connected to the CPU, and may be one or more of a readily available memory, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. Software instructions and data can be coded and stored within the memory for instructing the CPU. The support circuits are also connected to the CPU for supporting the processor in a conventional manner. The support circuits may include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like. A program (or computer instructions) readable by the system controller 101 determines which tasks are performable on a substrate. Preferably, the program is software readable by the system controller 101, which includes code to generate and store at least substrate positional information, the sequence of movement of the various controlled components, substrate inspection system information, and any combination thereof.

In one embodiment, the two printing heads 102 utilized in the system 100 may be conventional screen printing heads available from Applied Materials Baccini S.p.A. which are adapted to deposit material in a desired pattern on the surface of a substrate 150 disposed on a processing nest 131 in position "2" or "4" during a screen printing process. In one embodiment, the printing head 102 includes a plurality of actuators, for example, actuators 105 (e.g., stepper motors or servomotors) that are in communication with the system controller 101 and are used to adjust the position and/or angular orientation of the screen net, or screen printing mask, 12 (not shown in Figures 1 and 2) disposed within the printing head 102 with respect to the substrate 150 being printed. In one embodiment, the screen printing mask 12 is a metal sheet or plate (e.g. made by stainless steel) with a plurality of holes, slots, or other apertures formed therethrough to define a pattern and placement of screen printed material on a surface of a substrate 150. In one embodiment, the screen printing mask 12 is made of a relatively flexible material, for example consisting of a mesh with a warp and weft structure. In one embodiment, the screen printed material 11 may comprise a conductive ink or paste, a dielectric ink or paste, a dopant gel, an etch gel, one or more mask materials, or other conductive or dielectric materials. In general, the screen printed pattern that is to be deposited on the surface of a substrate 150 is aligned to the substrate 150 in an automated fashion by orienting the screen printing mask 12 using the actuators 105 and information received by the system controller 101 from the inspection system 200. In one embodiment, the printing heads 102 are adapted to deposit a metal containing or dielectric containing material on a solar cell substrate having a width between about 125 mm and 156 mm and a length between about 70 mm and 156 mm.

In some embodiments, the net, or screen printing mask, 12 (Figures 3 - 7) normally consists of a sheet 14 which is supported by a peripheral frame 16. The sheet 14, in its inactive condition, lies on a theoretical horizontal first lying plane "PI", shown by dashes in the attached drawings.

In a known manner, and by means of known motorization or translation means, such as a linear movement actuator 38, partly visible in Figure 7, the blade device 10 can be made to linearly advance on the net 12 with an alternate linear movement, indicated by the arrow "F" in the attached drawings, to carry out the desired printing operation.

For example, the linear movement actuator 38 can be configured as the above- mentioned actuators 105 (Figure 2).

Normally, the blade device 10 of the invention is moved in a first direction, for example as indicated by arrow "F" in Figures 3 - 6, to carry out the printing, whereas in the return travel no printing is done and the accumulated print material is recovered. There is nothing to exclude that, with suitable strategies, printing may be carried out in both directions.

The blade device 10 in this case comprises a frame 20 to support a print extremity 18 that act as a squeege. The blade device 10 defines a second plane "P2" represented by the lying plane of the relative frame 20.

The first theoretical lying plane "PI" of the net 12 and the second plane "P2" of the blade device 10 form a first angle between them, indicated by the letter "al" for convenience only in Figure 3.

The print extremity 18 is able to act on the upper surface of the central sheet 14, so as to spread the print material 1 1, with a determinate printing pressure, which is progressively delivered and so as to define the conductive tracks on the substrate 150 below.

With the solution according to the invention, it is possible to use any kind of paste suitable for silk-screen printing that is commercially available on the market, for example based on a metallic material (silver, aluminum or other), a dopant paste or an etching paste.

As can be seen in the attached drawings, the print material 11 is delivered downstream of the blade device 10 with respect to the direction of advance of the blade device 10, indicated by the arrow "F", or with respect to the opposite direction.

The angle formed by the surface of the sheet 14 varies dynamically following the deformation of the flexible material which makes up the sheet, due to the pressure exerted by the printing extremity 18 during printing. In some embodiments, the pressure exerted by the printing extremity 18 could be determined by the actuators 105 of the printing head 102 as described above. The situation in which the sheet 14 is deformed in the course of printing is shown in Figures 3 - 6, schematically and deliberately disregarding the real proportions between the entity of the deflection and the sizes of the net, in order to facilitate comprehension. In particular, according to where the printing action takes place, closer to the frame 16, first and fourth operating condition shown in Figures 3 or 6, or in a more central position, second and third operating condition in Figures 4 or 5, the entity of the deformation sustained by the sheet 14 varies.

The blade device 10 is positioned on the net 12 so that the second plane "P2" defines a determinate second printing angle "a2" with respect to a portion 34 of the actual surface of the sheet 14 that deforms as it inclines during printing.

The second printing angle "a2" is defined, for example, according to parameters such as the intrinsic flexibility of the net 12 and the rheological properties of the print material.

In any case, according to the present invention, the desired second printing angle "ot2" between the second plane "P2" of the blade device 10 and the portion 34 of the inclined surface of the sheet 14 is calculated with an optimum value of amplitude according to the printing operation to be carried out and the quality of the printing to be obtained.

In the present description, the second printing angle "a2" is referred and determined in particular with respect to a portion 34 of the surface of the sheet 14 on which the print material 1 1 is progressively delivered, downstream of the blade device 10 with respect to the movement indicated by the arrow "F", and similarly also with respect to the movement in the opposite direction.

In operating conditions, the portion 34 of the surface of the sheet 14, inclined because of the flexibility of the material which makes it up, during printing, does not coincide with the theoretical first plane "PI" on which the sheet 14 lies at rest. As is known, this would determine an unwanted and involuntary dynamic variation of the second printing angle "ot2".

To compensate the dynamic angular variation between the portion 34 of the surface of the sheet 14 on which the printing extremity 18 acts and the second plane "P2" on which the blade device 10 lies, and to keep constant the relative second printing angle " 2", the blade device 10 is configured to be selectively rotated, automatically by means of the system controller 101, as indicated by the arrow G, in a manner consistent with the necessary angular compensation and thus to define constant delivery conditions and a uniform and desired printing speed of the print material 1 1. However, the maintenance at a constant value of the second printing angle "a2" between blade device 10 and portion 34 of the surface of the sheet 14 during printing entails the variation of the first angle "otl" formed by the blade device 10 and by the first theoretical horizontal lying plane "PI" of the sheet 14 of the net 12.

To this purpose, according to one form of embodiment, the blade device 10 is provided with movement means 25, for example of a mechanical, electromechanical or other type (e.g., stepper motors or servomotors), able to determine the rotation of the blade device 10 so that, during printing, it can follow and therefore compensate the variation in inclination of the portion 34 of the upper surface of the sheet 14, keeping the second printing angle "a2" at a fixed value during printing operation. Advantageously, the activation of the movement means 25 is totally autonomous with respect to the activation that allows the alternate linear movement means of the blade device 10 on the net 12 indicated by the arrow "F.

In some forms of embodiment, the movement means 25 comprise a motor 22 (e.g., stepper motors or servomotors) and a linear actuator 24, rotatably connected by means of an articulation member or other angular release element, 26, to the frame 20 of the blade device 10.

The motor 22 determines an alternate movement of the linear actuator 24 which, thanks to the articulation member 26, is transformed into the desired movement of rotation of the blade device 10.

The movement means 25 can be activated by the system controller 101 at the beginning of the printing operation to define a desired angular position of the blade device 10, for example different on each occasion according to the type of net 12 and/or the type of print material 1 1.

In this case, at least another articulation member 26 of the blade device 10 may be provided, for example between the frame 20 and the printing extremity 18, to allow an automatic adaptation of the angular position of the blade device 10 with respect to the net depending on the greater or lesser rigidity of the sheet 14, which meets the printing extremity 18 as it passes from the periphery toward the central zone of the sheet 14 and vice versa, in the movement indicated by the arrow "F".

In other words, the other articulation member 26 would allow a reciprocal inclination of the printing extremity 18 and the frame 20 to achieve an automatic adaptation of the angular position of the second plane "P2" according to the progressive inclination of the portion 34 of the upper surface of the sheet 14.

As an alternative to or in combination with the above, the movement means 25 can be selectively activated by the system controller 101 in the course of the printing operation to vary dynamically the angular position of the blade device 10.

This can be done, for example, according to the different depths at which the blade device 10 can be found when it is moved along the mesh of the net 12, due to the deflection of the sheet 14 and/or the angular variations that would occur because of the variation in height due to the presence or absence of emulsion and/or the different depths/heights of warp and weft.

In particular, the movement means 25 of the blade device 10 can receive command and control signals supplied by sensor means 28 (visible only in Figure 1), for example a sensitive element or pressure or inclination detector, which detects desired data relating to the variation in the reciprocal angular position between the blade device 10 and the deformed surface of the sheet 14, due both to the macroscopic deflection of the net 12, and also the microscopic variation in depth due to the differences in height between warp and weft.

For example, the command signals supplied by said sensor means can be indicative of the variations in depth of the blade device 10 along the net 12 with respect to the first theoretical plane "PI", or of the relative angular variations between the blade device 10 and the inclined portion 34 of the surface of the sheet 14, or of the dynamic variations in inclination of the deformed portion 34 of the surface of the sheet 14, or again said signals supplied by said sensor means can be indicative of the position of the blade device 10 inside the net 12 or of the variation in deflection of the sheet 14, for example closer to or farther from the frame 16 or the central region of the sheet 14.

In any case, the command signals supplied by said sensor means, advantageously processed by said system controller 101 that manages everything, determine the selective and automatic activation of the movement means 25 to rotate the blade device 10 consistently for the purposes of the angular compensation as above, or in any case to define dynamically a desired angle of incidence of the blade device 10. Then, the system controller 101 provides for keeping the selected second printing angle "a2" at a constant value during printing operation.

Figure 7 shows another form of embodiment of the blade device 10 according to the invention, alternative to the embodiments depicted in Figures 3 - 6. In Figure 7 part of said linear movement actuator 38 is visible, which allows the movement of the blade device 10 in the direction indicated by the arrow "F" in Figures 3 - 6. Moreover, in this embodiment, the above mentioned movement means 25 comprise a cylindrical actuator 27 provided with a motor reducer, which functions as a motorization mean for rotation, and also as a cylindrical articulation element between the frame 20 of the blade device 10 and the linear movement actuator 38. In this solution too, the movement means 25 are advantageously controlled by the system controller 101.

Figures 8 - 13 disclose further embodiments of the blade device 10 of the present invention.

In some forms of embodiment disclosed in Figures 8 - 10, the blade device 10 also comprises one or more member for the flooding or recovery of the print material 1 1 and/or for cleaning, of the mechanical type, which is integrated in correspondence with the print extremity 18, and therefore located above the net 12.

According to some forms of embodiments of the present invention, since the mechanical-type flooding or recovery and/or cleaning member is integrated with the print extremity 18, it thus acts selectively on the same surface on which the print extremity 18 itself acts, in this case above the sheet 14 of the net 12.

Moreover, since the one or more recovery and/or cleaning members are integrated with the blade device 10 which acts above the net 12, do not cause any problems of bulk nor are they constrained to the limited spaces that normally exist around the above mentioned printing head 102.

In some embodiments, the blade device 10 has at least an operating condition for printing (Figure 8), in which the print extremity 18 acts on the net 12, and an operating condition for recovery and/or cleaning (Figures 9 and 10), in which the flooding or recovery and/or cleaning member recovers the material and/or cleans the net 12.

In this case, the blade device 10 is selectively rotatable between the operating condition for printing and the operating condition for recovery and/or cleaning (as indicated by the arrow "G" in Figures 9 and 10).

In the operating condition for printing the blade device 10 can be used for printing inasmuch as, thanks to a suitable inclination of the blade device 10, the print extremity 18 is in an active position for acting on the sheet 14.

In the operating condition for recovery and/or cleaning, the blade device 10 can be used to recover the print material, or for the mechanical cleaning of the sheet 14 of the net 12, since, thanks to a different angular position, the integrated mechanical-type recovery and/or cleaning member is in an active position to act to recover or clean the sheet 14, whereas the print extremity 18 is in an inactive position, separated from the sheet 14.

Figures 9 and 10 show two different symmetrical geometric positions of the blade device 10 in the operating condition for recovery and/or cleaning at the edges of the net 12.

Advantageously, when it is necessary to recover material, or to clean the net, the blade device 10 is rotated and clamped in a desired angular position and then it is made to translate, by means of the linear movement actuator 38, along the net 12, in the direction of the arrow "F", normally in the opposite direction to the direction in which the printing operation took place.

According to a variant, the blade comprises one flooding or recovery member on one side and the print extremity 18 on the other side.

According to another variant, as shown in Figures 8 - 10, the blade device 10 comprises two flooding or recovery members disposed on opposite sides with respect to the print extremity 18.

Another variant provides that the blade device 10 comprises a flooding or recoveiy member and a cleaning member disposed on opposite sides with respect to the print extremity 18.

According to another variant the recovery and/or cleaning member comprises a single flooding or recovery blade 32. According to another variant, the recovery and/or cleaning member is formed by two flooding or recovery blades 32 disposed in this case symmetrically on opposite sides outside with respect to the print extremity 18. In this way, the print extremity 18 is in a central position and is partly enclosed between the two blades 32.

According to another variant, the recovery and/or cleaning member comprises a flooding or recovery blade 32 on one side with respect to the print extremity 18 and a cleaning blade on the other side.

Advantageously, in the case of the cleaning operation, the auxiliary use of a suitable solvent may be provided, which is sprayed or in some way delivered and which softens the accumulated print material, facilitating the removal thereof.

By angularly orientating the blade device 10, it can be aligned so that the flooding blade 32 can supply print material for printing, then the blade device 10 can be positioned to perform the printing operation using the print extremity 18 (Figure 8) and then recover the left over printing material 1 1 using the recovery and/or cleaning blade 32 (Figures 9 and 10).

According to a variant, the two blades 32 can be positioned at a desired angle or moved relative to the net 12, to define different geometric configurations, for example depending on the type or quantity of print material to be recovered or the cleaning to be done.

According to one form of embodiment, each flooding blade 32 consists of a first segment 35 which extends transversely, in this case for example at about 90°, from the lower part of the frame 20, a little above the print extremity 18, and of a second scraping segment 36, connected transversely to the first segment 35, in this case for example also at about 90°, which extends toward the sheet 14 below.

The conformation of the flooding blade 32 is thus such as to surround externally part of the print extremity 18, leaving the space for a window, or aperture 40, that is defined between the two free ends of the second segments 36 of the two flooding blades 32 mounted in correspondence with the print extremity 18.

The shape and size of the two second segments 36 are such that part of the print extremity 18 extends beyond the second segments 36 by a determinate amount, and thus protrudes from the window 40.

For example, in the case where the cross section of the print extremity 18 is substantially quadrangular, the geometrical shape of the two flooding blades 32 that partly enclose the print extremity 18 will be of a mating quadrangular shape, and therefore very compact, as can be seen in the attached drawings, with the provision, however, of leaving a free space of suitable size to define the window 40 through which the print extremity 18 protrudes.

In this way, the blade device 10 can be used in the operating condition for printing as for example shown in Figure 8, for the printing operation, providing to orient the blade device 10 angularly so that the window 40 is directly facing (Figure 8) the sheet 14 and so that the window 40 defines an ideal lying plane substantially parallel to the sheet 14.

In this way, the print extremity 18 protrudes outside the two flooding blades 32 and can come into contact with the sheet for the printing operation.

Moreover, by rotating the blade device 10 in the operating condition for recovery and/or cleaning, the window 40 does not directly face toward the sheet 14, since it has its own ideal lying plane deliberately inclined with respect to the sheet 14, as indicated in Figure 9 or Figure 10.

Consequently, the print extremity 18 is lifted from the sheet 14 and one or the other of the two flooding blades 32, in this case the relative second segment 36, is brought into contact with the sheet 14 so as to achieve the mechanical action to recover the material and/or to clean.

Once the blade device 10 has been rotated and clamped in the desired angular position, by said system controller 101 that controls said movement means 25 associated with the blade device 10 (as described hereinbelow), the operation to recover material and/or clean is conducted by moving the blade device 10 linearly.

In some embodiments, the linear movement of the rotated blade device 10 along the net 12 is obtainable, for example, by using the same translation means, in this case the linear movement actuator 38, used to move the blade device 10 in the direction of the arrow "F" and to print the print material 11 through the net 12, but in the opposite direction. In some embodiments, in said operating condition for recovery and/or cleaning, the window 40 is distanced from the net 12 so that the print extremity 18 is separated from the net and one of the recovery and/or cleaning members 32 can act on the net 12. According to one form of embodiment of the present invention, the angular rotation of the blade device 10 can be obtained automatically by said movement means 25.

Figures 1 1, 12 and 13 show another form of embodiment of the blade device 10 according to the invention, alternative to the embodiment depicted in Figures 8 - 10. In particular, in Figure 1 1 part of said linear movement actuator 38 is visible, which allows the movement of the blade device 10 in the direction indicated by the arrow "F", also as represented in Figures 8 - 10.

Moreover, in this embodiment, the movement means 25 comprise a cylindrical actuator 27 provided with a motor reducer, which functions as a motorization mean for rotation, and also as a cylindrical articulation element between the frame 20 of the blade device 10 and the linear movement actuator 38 which determines the linear translation (arrow "F") of the blade device 10. In this solution too, the movement means 25 can be advantageously controlled by the system controller 101.

The present invention therefore provides a single actuator, linear actuator 24 or cylindrical actuator 27 according to the different embodiments, and two distinct commands to pass between the two operating conditions as above, of which a first command determines the operating condition for printing and a second command determines the operating condition for recovering the material and cleaning the net. The two commands are advantageously driven by means of said single actuator that determines the desired movement to pass from one operating condition to the other.

Figures 12 and 13 in particular show the part of the blade device 10 where there is the integration of the recovery and/or cleaning member, in this case a single blade 32 to recover the material, and the print extremity 18. In this case, the blade 32 consists of a central segment or wall 41 and of two curved extremities 43, advantageously shaped to laterally contain the material recovered. In this case, the print extremity 18 is associated with a connection element 21 which cooperates, by means of attachment means, with a lower connection end 19 of the support frame 20. Moreover, a transverse connection segment or plate 39 extends from the connection element 21 attached to the lower connection end 19 of the frame 20. From the connection plate 39 the central wall 41 of the blade 32 extends transversely downward. In this way the connection plate 39 positions and supports the blade 32, substantially next to the print extremity 18.

It is clear that by providing, according to a variant not shown in the drawings, two blades 32 disposed on opposite sides to the print extremity 18, it is in any case possible to define, thanks to the conformation of the connection plate 39 and the central wall 41 of the blade 32, the window 40 that allows the print extremity 18 to protrude, as we said with reference to Figures 8, 9 and 10.

Advantageously, according to one embodiment of the invention, the passage from the operating condition for printing to the operating condition for recovery and/or cleaning is synchronized with the overall printing cycle, for example managed by a suitable system controller 101.

Consequently, the system controller 101 can command, in a synchronous manner, both the linear movement actuator 38 and also the movement means 25 which determine in this case the rotation of the blade device 10.

Preferably, the operation to recover the material can be started, after the printing action, once the appropriate signals, supplied from control sensors, indicate that a printing pass has been carried out and therefore it is necessary to recover the accumulated print material. This can be synchronized automatically, by means of the system controller 101, with the printing cycle provided, advantageously providing an operation to recover the material after every printing pass.

Furthermore, the cleaning operation can be started according to signals sent and processed by the system controller 101 and indicating, directly or indirectly, that the net is dirty. The signals can derive from a direct assessment of excess print material and therefore dirt on the net, for example by means of optical sensors that detect variations in the optical properties of the net, or mechanical sensors that detect variations in the elasticity of the net, or from an indirect assessment, for example taking information from a control system by means of video detection which scans the print supports produced in order to identify imperfections or printing errors which do not meet the required quality standards, indicating to the system controller 101 that it is necessary to start the recovery of the material and/or clean the net 12. Alternatively or in combination, the system controller 101 may be configured and pre-set to start cycles to recover the material and/or clean at regular intervals, and in any case settable, even manually or forcedly by an operator.

There is nothing to exclude, according to a simple solution of the present invention, not automated or partly automated, that the rotation of the blade device 10 in order to pass from the printing condition to the condition for recovery and/or cleaning, and vice versa, is set manually by an external operator.

It is clear that modifications and/or additions of parts and/or steps may be made to the blade device 10 for silk-screen printing on a print support and the relative printing method as described heretofore, without departing from the field and scope of the present invention.

It is also clear that, although the present invention has been described with reference to specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of blade for silk-screen printing on a print support and the relative printing method, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

Claims

1. Blade device for the silk-screen printing of one or more print tracks on substrates, or print supports, (150) by means of a print material (1 1) able to be deposited on a net (12) comprising a sheet (14) that defines, in its inactive condition, a first lying plane (PI), comprising:

- a printing extremity (18) able to act with pressure on an upper surface of said sheet (14) to determine the printing of the print material (1 1) through the net (12);

- a frame (20) able to support said printing extremity ( 18) and lying on a second lying plane (P2) which defines a determinate first angle ("al") with respect to said first plane (PI);

- a linear movement actuator (38) to make linearly advance said blade device on the net (12) with an alternate linear movement, to cany out the desired printing operation;

characterized in that it comprises movement means (25) able to determine the selective rotation of said blade to selectively vary the inclination thereof with respect to said first lying plane (PI), to define one or more desired angulations with respect to a portion (34) of the upper surface of the sheet (14) on which the print material (1 1) is progressively delivered, the activation of said movement means (25) being autonomous with respect to the activation of said linear movement actuator (38), said movement means (25) being configurable to maintain constant a second angle ("<x2") between the second lying plane (P2) of the frame (20) and said portion (34) of the upper surface of the sheet (14), which portion (34) is inclined with respect to said first angle ("al") following the deformation of the sheet (14) due to the action of the printing extremity (18), the blade device further comprising sensor means (28) suitable for detecting desired data relating to the variation in the reciprocal angular position between the blade device and the deformed surface of the sheet (14), a system controller (101) being provided, able to automatically control and command the rotation of said blade according to signals received from said sensor means (28) relating to the reciprocal angular position of said blade and said portion (34) of the surface of the sheet (14).

2. Blade device as in claim 1, characterized in that said movement means (25) comprises a cylindrical actuator (27).

3. Blade device as in claim 1 , characterized in that said movement means (25) comprise motor means (22) rotatably constrained, by means of an articulation member (26), to said blade device.

4. Blade device as in any claim hereinbefore, characterized in that it also comprises at least a flooding or recovery and/or cleaning member (32), integrated therewith, to recover the print material (1 1) and/or to clean the excess print material (11) from the net (12), and in that it has at least an operating condition for printing in which said print extremity (18) is able to act on the net (12) and at least an operating condition for recovery and/or cleaning in which said flooding or recovery and/or cleaning member (32) is able to act on the net (12) to recover the material and/or clean the net (12).

5. Blade device as in claim 4, characterized in that it is selectively movable to pass from the operating condition for printing to the operating condition for recovery and/or cleaning and vice versa.

6. Blade device as in claim 4 or 5, characterized in that said print extremity (18) and said flooding or recovery and/or cleaning member (32) are reciprocally movable in order to pass from the operating condition for printing to the operating condition for recovery and/or cleaning and vice versa.

7. Blade device as in any claim hereinbefore, characterized in that said movement means (25) are able to automatically determine the passage from the operating condition for printing to the operating condition for recovery and/or cleaning and vice versa.

8. Blade device as in claim 7, characterized in that said movement means (25) are able to determine the selective rotation of said blade between the operating condition for printing to the operating condition for recovery and/or cleaning.

9. Blade device as in claim 7 or 8, characterized in that said movement means (25) are able to determine the reciprocal movement of said print extremity (18) and said flooding or recovery and/or cleaning member (32) in order to pass alternately from the operating condition for printing to the operating condition for recovery and/or cleaning and vice versa.

10. Blade device as in any claim hereinbefore, characterized in that said print extremity (18) and said flooding or recovery and/or cleaning member (32) are positioned and supported by means of a common support frame (20).

11. Blade device as in any claim hereinbefore, characterized in that it comprises at least two flooding or recovery and/or cleaning members (32) disposed on opposite sides with respect to the print extremity (18).

12. Blade device as in claim 1 1, characterized in that it comprises two flooding or recovery members disposed on opposite sides with respect to the print extremity (18).

13. Blade device as in claim 1 1, characterized in that it comprises a member to recover the print material (11) on one side with respect to the print extremity

(18), and a cleaning member on the opposite side with respect to the print extremity (18).

14. Blade device as in any claim from 1 1 to 13, characterized in that said two flooding or recovery and/or cleaning members (32) are disposed in substantial correspondence with said print extremity ( 18), on opposite sides with respect to said print extremity (18) and conformed so as to define a window (40) through which said print extremity (18) protrudes.

15. Blade device as in claim 14, characterized in that in said operating condition for printing, the window (40) faces toward the net (12) so that said print extremity (18) can act on said net (12), whereas said flooding or recovery and/or cleaning members (32) are separated from said net (12), and in that, in said operating condition for recovery and/or cleaning, the window (40) is distanced from the net (12) so that said print extremity (18) is separated from said net (12) and in that one of said flooding or recovery and/or cleaning members (32) can act on said net (12) in order to recover the material and/or for cleaning.

16. Blade device as in any claim hereinbefore, characterized in that said recovery and/or cleaning member comprises at least a blade, scraper, scraping spatula or knife (32) able to recover the print material (11) and/or mechanically clean the net (12).

17. Blade device as in claim 14, characterized in that the flooding or recovery and/or cleaning members comprise two blades, scrapers, scraping spatulas or knives (32), each of which consists of a first segment (34, 39) which extends transversely on opposite sides with respect to the print extremity (18) and of a second segment (36, 41) which extends transversely from said first segment (34, 39) toward said print extremity (18), so as to partly surround said print extremity (18) and define said window (40).

18. Printing head for the silk-screen printing of one or more print tracks on print supports comprising a blade device as in any claim hereinbefore.

19. Method for the silk-screen printing of one or more print tracks on print supports by means of a print material (1 1) deposited on a net (12) formed by a sheet (14) that defines, in its inactive condition, a first lying plane (PI), comprising a step of acting with pressure on an upper surface of said sheet (14) to determine the printing of the print material (1 1) through the net (12) by means of a blade device (10) having a print extremity (18) that is supported lying on a second lying plane (P2) which defines a determinate first angle ("al") with respect to said first plane (PI), a step of linearly advancing the blade device (10) on the net (12) with an alternate linear movement, to carry out the desired printing operation, characterized in that it comprise the step of rotating said blade device (10) to selectively vary the inclination thereof with respect to said first lying plane (PI), to define desired angulations with respect to a portion (34) of the upper surface of the sheet (14) on which the print material (11) is progressively delivered, the step of rotating being performed to maintain constant a second angle ("a2") between the second lying plane (P2) of the frame (20) and said portion (34) of the upper surface of the sheet (14), which portion (34) is inclined with respect to said first angle ("al") following the deformation of the sheet (14) due to the action of the printing extremity (18), the rotation of said blade device (10) being automatically controlled and commanded, autonomously with respect to the step of linearly advancing the blade device (10) on the net (12), according to signals received relating to the reciprocal angular position of said blade and said portion (34) of the surface of the sheet (14).