"METHOD TO PRODUCE A PRINTING STENCIL FOR THE DECORATION, BY WRITINGS AND/OR IMAGES, OF PRINTING SUPPORTS, STENCIL THUS ACHIEVED AND PRINTING DEVICE PROVIDED WITH SAID STENCIL"

FIELD OF THE INVENTION

The present invention concerns a method to produce a printing stencil in order to decorate, by writings and/or images, printing supports, such as ceramic tiles, surfaces made of glass, fabric, wood, paper or any other material similar or comparable to these. In the following description, the term images is used to indicate any decoration, design or form, in one color or multi-colored, applicable on a printing support. The present invention also concerns the stencil made by means of this method and the printing device provided with this stencil. BACKGROUND OF THE INVENTION The use of a printing stencil in a printing device to decorate printing supports, such as ceramic tiles, with writings and/or images is known. The printing devices typically comprise a mobile support plane along which the supports are translated in the direction of a motorized cylinder, located above said plane. The cylinder rotates around its own axis and the printing stencil is associated or made in a single piece on its surface.

The printing stencil usually comprises a layer of elastomer material, typically silicone, on one surface of which, by means of laser engraving techniques, the writings and/or the images that are transferred due to contact between this surface and each support that is to be printed are engraved. This transfer is achieved by means of inks and/or glazes with a high coloring oxide content previously applied to said surface of the printing stencil.

One disadvantage of the known printing stencil is that the laser engraving techniques used to achieve this need to use expensive equipment which requires highly specialized technical assistance and laborious and frequent maintenance operations. Moreover, the layer of elastomer material that makes up the printing stencil, or the cylinder in its entirety, if the printing stencil is made all in one piece with it, must be sent to appropriate laboratories, provided with such equipment, to make the engraving, with all the costs of transport, storage and

work which this involves.

The cylinder causes a considerable bulk and furthermore, if the printing stencil is made all in one piece with it, when the efficiency of its printing is finished due to wear, it must be completely replaced, with considerable costs due to the disposal of the used cylinder and the long time taken deriving from the organizational difficulties for its replacement which this entails.

One purpose of the present invention is to define a method to produce a printing stencil for the decoration, by writings and/or images, in particular of tiles and/or other similar or comparable surfaces, which allows to contain the costs in terms of material, equipment used, transport and storage.

Another purpose of the present invention is to produce a printing device provided with said printing stencil which determines both a reduced bulk and weight and which does not need laborious and frequent maintenance operations.

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 purposes, the present invention concerns a method to produce a printing stencil, or more in general image transfer means, for the decoration by writings and/or images of printing supports such as, for example but not only, ceramic tiles or other similar supports, on which ink or glaze is able to be applied, able to transfer, by contact with said printing supports, said writings and/or images onto said printing supports.

According to a characteristic feature of the present invention, the method comprises at least a step of stencil molding in which at least a first layer for the transfer of the images, provided with a printing surface and comprising gelatin and/or photo-engravable emulsion, at least a second support layer, for example a silk-screen fabric or suchlike, and at least a third anti-leakage layer, comprising a polmerizing film and able to prevent the leakage of said ink and/or said glaze, are associated with each other to form a single multi-layered photo-engravable

element, which constitutes the basic body of the stencil.

According to a variant of the present invention, the stencil molding step comprises at least a first sub-step in which said second support layer is leveled and said gelatin and/or emulsion is disposed in a uniform way on said second support layer.

According to another variant of the present invention, the stencil molding step comprises at least a second sub-step in which the third anti-leakage layer is associated with the gelatin or emulsion, in a position opposite to the printing surface, and with the second support layer, and then said third layer is dried. According to a further variant of the present invention, the stencil molding step comprises at least a third sub-step in which the writings and/or images are engraved in correspondence with said first image transfer layer by means of photo-engraving techniques and/or photo-catalyzation.

The method according to the present invention therefore allows to obtain a single element of the desired size, to form a stencil able to be subsequently subjected to photo-engraving in order to make engravings which make up the writings and/or images which have to be transferred onto the printing supports.

The use of the third anti-leakage layer, as well as preventing leakage and/or the seepage of the ink in the printing step, thus preventing waste, confers greater elasticity and flexibility to the second support layer. The third anti-leakage layer also functions as an aggregation element for the three layers and therefore enables the formation of a single element, less bulky, easier to stock and transport.

The use of a silk-screen fabric and of photo-engravable gelatin or emulsion also allows to contain costs, both in terms of materials, given the easy availability of the fabric and of the gelatin and/or emulsion, and also in terms of equipment used. In fact, the method according to the present invention does not need sophisticated apparatus required in laser engraving used in the state of the art.

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: - fig. 1 is a view in section of a printing stencil obtained using the method

- A -

according to the present invention;

- fig. 2 is a first variant of the printing stencil in fig.1 ;

- fig. 3 is a second variant of the printing stencil in fig.l;

- fig. 4 is a schematic representation of a printing device which uses a printing stencil obtained using the method according to the present invention;

- fig. 5 is a schematic representation of a variant of the printing device in fig. 4.

DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF

EMBODIMENT With reference to the attached drawings, a printing stencil 10, or printing plate, according to the present invention is used for the decoration, by writings and/or images, of supports such as tiles or other surfaces, made of glass, fabric, wood, paper or any other similar or comparable material. On the printing stencil 10 glazes or inks, with a water base, or any other type of glaze or ink suitable for the purpose can normally be applied, such as for example glaze or ink of the type used in silk-screen printing processes, consisting for example of glass glaze and ceramic pigments homogenized in an aqueous base consisting of glycols and soluble resins. The device delivering the ink, of a suitable color, is of the known type and is not shown in the drawings, inasmuch as it is irrelevant for the understanding of the present invention. The printing stencil 10 according to the present invention is able to be used in printing devices 17 (figs. 4 and 5) comprising pairs of rotating rollers 18, or a rotating cylinder, on which the printing stencil 10 is wound, and a mobile support plane 19 on which the support to be printed is disposed, in this case a tile 20, to be taken, in a pre-established direction, indicated in fig. 4 by the arrow A, in correspondence with the printing stencil 10. In the solution shown in fig.4 the printing stencil 10, wound between the pair of rollers 18, is disposed vertically above the mobile support plane 19, and is able to rotate in the direction indicated by the arrow B.

According to a variant embodiment shown in fig.5, the printing stencil 10 is disposed horizontally above the mobile support plane 19, substantially parallel to the tile 20 to be decorated.

In this embodiment the contact between the printing stencil 10 and the tile 20 is achieved with the help of a pressure roller 21 which, sliding in the directions

indicated by the arrows C and D, creates a contact zone between the printing stencil 10 and the tile 20. This solution is advantageous for making decorations on panels and/or individual tiles 20 of bigger sizes.

The printing stencil 10 comprises a first image transfer layer 11, able to come into direct contact, by means of a first surface thereof, otherwise called printing surface 11a, with the support to be printed. The first image transfer layer 11 comprises gelatin, or silk-screen emulsion, catalyzed and resistant to water on which, as will be described hereafter, the engraving of the writings and/or the images to be transferred to the support is achieved. The printing stencil 10 also comprises a second support layer 12, comprising a calibrated fabric of the type used in the known processes of silk-screen printing, made for example of polyester or, as an alternative, of metal, with which the first transfer layer 11 is associated.

The printing stencil also comprises a third anti-leakage layer 13 to prevent the leakage of the ink or the glaze associated with the second support layer 12 and with the first layer 11, through the meshes of the silk-screen fabric, and disposed substantially on the surface 12a of the second support layer 12 opposite the surface on which the first image transfer layer 11 is. The third anti-leakage layer

13 comprises a polymerizing film made of polyester, polyethylene, polypropylene or any other comparable material. In particular the film formed by the third anti-leakage layer 13 is solid with the gelatin, or catalyzed silk-screen emulsion, of the first image transfer layer of 11.

According to a variant, the third anti-leakage layer 13 is made by depositing suitable varnishes and/or substances with a gelatinous consistency, for example polyurethane varnishes or varnishes provided with synthetic polymers, and/or lacquers, or waxes, single-component or with several components, with a high resistance to solvents.

The anti-leakage layer 13 is also able both to prevent the seepage and the leakage of the glaze or the ink used for the transfer of the writings and/or the images from the printing stencil 10 to the support, and also to give elasticity to the second support layer 12.

The printing stencil 10 comprising the three layers 11, 12, 13 thus associated, is flexible and elastic and such that each layer 11, 13 cannot be removed from

layer 12. The printing stencil 10 is thus able to consist, in fact, of one single sheet, or a multi-layered photo-engravable lamina.

According to a variant, the printing stencil 10 is shaped in a subsequent step so as to define a ring profile. In a preferential form of embodiment, the printing stencil 10 also comprises a further layer, not shown in the drawings, associable to the first image transfer layer 11, comprising a protective film made of silicone paper or polyacetate, to protect the printing surface 1 Ia.

In a further preferential form of embodiment, a support layer made of elastomer material is associable with the printing stencil 10, such as rubber, neoprene, polybutadiene, silicone, wound on the pair of rollers 18, or on a rotating cylinder, and applicable behind the third layer 13.

The support layer of elastomer material, because of its elastic deformability, allows to transfer the writings and/or the images even if there are irregularities in the surface of the tile 20, guaranteeing, under any condition, a perfect adherence of the printing stencil 10 and the surface of the tile 20.

To achieve the printing stencil 10 described heretofore proceed as follows.

The surface of the silk-screen fabric of the second support layer 12 is first made level and regular, for example, by using tensioning means. The tension to which the silk-screen fabric has to be subjected is variable depending on the type of silk-screen fabric used.

Subsequently the gelatin or emulsion of the first image transfer layer 11 is deposited by means of an applicator device. The gelatin or emulsion is applied on the silk-screen fabric in correspondence with the surface 12a. Due to the effect of gravity the gelatin applied tends to be disposed in greater quantities on the surface opposite surface 12a, and therefore the printing surface 1 1a is formed facing downward.

To obtain the desired thickness of the gelatin or emulsion, several layers of gelatin or emulsion are applied on surface 12, disposed one on top of the other when the gelatin or emulsion is still damp.

According to a variant it is possible to achieve the desired thickness of gelatin by initially applying a first layer of gelatin deposited on the silk-screen fabric as described above, and then, after it has dried, at least a second or more layers of

gelatin in correspondence with the printing surface 11a.

Furthermore, the gelatin or emulsion is distributed homogenously on the silk- screen fabric due to the surface tension of the gelatin or emulsion itself, forming a surface substantially free of depressions or porosity. Subsequently the thickness of the gelatin obtained is dried.

According to another variant of the present invention, it is possible to provide for the use of films or sheets of gelatin, otherwise called "capillary films", having pre-defined thicknesses. These "capillary films" are applied on the silk-screen fabric after it has been dampened. Alternatively the "capillary films" can also be applied on pre-existing layers of gelatin on the printing surface 11a.

After the gelatin is completely dry, the third anti-leakage layer 13 is deposited on the surface 12a. The three layers 11, 12, 13 thus associated are then subjected to drying until the third anti-leakage layer 13 is also completely dry, to form a substantially protective film. The printing stencil 10 thus obtained is therefore a single multi-layered lamina or sheet, ready to be stored and/or sent to the users, and to be subjected to a photo-engraving method. By means of photo- engraving, in correspondence with the printing surface 11a, the engravings 14 of the writings and/or images to be printed are achieved, which will accommodate the printing glaze or ink. According to a variant embodiment of the present invention, the printing stencil 10 is made by disposing the third anti-leakage layer 13 in a homogenous manner in correspondence with the surface 12a of the silk-screen fabric.

The third anti-leakage layer 13, thus deposited, is then dried to form the protective film able to prevent the leakage and/or the seepage of the ink or the glaze.

In correspondence with the surface opposite the surface 12a, at least a layer of gelatin is associated with the film, which is subsequently subjected to drying.

It is clear that modifications and/or additions of parts may be made to the printing stencil 10 as described heretofore, without departing from the field and scope of the present invention.

It falls within the field of the present invention to provide, instead of the silk- screen fabric and the third anti-leakage layer 13, to use at least a support layer 15 (fig. 3) made of polyester, nylon and/or other comparable materials, provided on

one of its surfaces with hollows 16 able to accommodate the gelatin and/or the emulsion. The hollows 16 are normally of a known geometric shape, for example hexagonal, otherwise known as honeycomb.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of printing stencil 10, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.