The invention relates to a process for realising matrices, in particular
for the decoration of ceramic tiles.
The prior art teaches matrices, used in the decoration and glazing
of ceramic tiles, made by engraving into elastically deformable surfaces arranged
on matrix-bearing surfaces, usually cylinders, equipped on rotary machines.
The matrix recesses are cut into smooth silicone-rubber cylindrical
surfaces and are constituted by a plurality of cells predisposed to retain small
quantities of glaze destined, in the decoration stage, to be transferred from the
cells onto the surface to be decorated, by contact between the surface to be decorated
and the surface of the smooth elastically-deformable cylinder.
The prior art also teaches laser-cutting of incisions in the elastic
surface of a drum in flexographic applications.
The latter process, however, requires the use of rather expensive
and sophisticated apparatus, which not insignificantly limits its use potential.
FR 2 419 819 discloses a process for making a gravure type of printing
plate whereby a metal or woven textile screen is coated with photosensitive material
which is imagewise exposed and developed to give a screen having a predetermined
A layer of metal is then applied such that the holes in the engraved
parts of the screen are closed off over a portion of their depth creating cavities
which give a recessed design.
For printing the cavities are filled with ink.
The main aim of the present invention is to obviate the limitations
in the prior art. An essential advantage of the invention consists in the fact that
it can be actuated within the normal and usual technology of photo-engraved silk
screen production. These aims and advantages and more besides are all attained by
the present invention, as it is characterised in the appended claims.
Further characteristics and advantages of the present invention will
better emerge from the detailed description that follows of a preferred but non-exclusive
embodiment of the invention, illustrated purely by way of a nonlimiting example
in the accompanying figures of the drawings, in which:
- figure 1 is an enlarged-scale view of a transversal section of an engraved silk
- figure 2 is the same section of figure 1, showing the screen obtained by application
of the process;
- figure 3 is the same section of figure 2 and shows the result of a second embodiment
of the invention;
- figure 4 schematically shows the use of the screen as a matrix for the decoration
of ceramic tiles.
With reference to the figures, 1 denotes in its entirety a normal
silk screen which has been etched according to a predetermined design.
Figure 1 shows the holes 4 which are not filled with "filler" 5 which
in the non-engraved zones occupies all of the space between the threads 3 and renders
the screen completely impermeable in these zones.
The preparation of the above-described screen constitutes the first
stage of the process of the present invention, which will be followed by a second
stage in which the holes 4 in the engraved zones will be closed on one side over
a portion of the breadth of the screen, so that on the opposite side, corresponding
to the engraved zones, cavities 2 are identified which all together give rise to
an engraved or etched design.
Before closing off, the engraved parts (i.e. the parts with the holes
4) of the screen can be treated with a waterproofing material, which has the task
of waterproofing the threads 3 of the screen 1 left uncovered, i.e. not covered
over by the filler material 5.
In the invention engraved parts of the screen 1 are waterproofed (to
protect the threads 3) after the holes 4 are closed off.
The waterproofing treatment is performed by means of a temporary filling
of the cavities in the engraved zones with a very fluid silicone-based material,
the threads 3 of the screen being thoroughly drenched, followed by an aspiration
(from one side of the screen 1) of the material until the previously-closed cavities
are re-opened, thus returning to the original engraved configuration.
In particular the closure on one side only of the screen 1 of the
holes 4 in the engraved zones concerns a portion of the depth of the screen 1 itself,
and generates a surface delimiting the cavities 2 but free of undercuts. Considering
that the threads 3 have a circular section, in order to eliminate undercuts it will
usually be sufficient to close the holes 4 by filling them up with material (e.g.
silicone rubber) over a large part of the depth of the screen, so that inside the
cavities 2 the threads 3 project for less than half of their thickness, leaving
no undercuts, as mentioned above.
The depth of the cavities 2 can be decided as needed, keeping constant
the depth of the material used to close the holes 4 off; it is sufficient simply
to apply an additional layer 6 (e.g. a layer of silicone rubber) to the side of
the screen destined to afford the cavities 2. The additional layer 6 is constrained
perfectly on the screen.
The screen can be used to decorate ceramic tiles 10 by a transfer
operation involving dosed quantities of glaze or colour, previously loaded onto
the screen and therefore contained in the cavities 2, and applied on the surface
to be decorated by pressing the screen onto the surface.
The screen obtained using the above-described process constitutes
a matrix, usable in particular for decorating ceramic tiles.
The engraved design, constituted by the totality of the cavities 2,
is filled with glaze at the start of each operational cycle, while the smooth external
surface 7 stays perfectly clean.
The matrix, with the cavities 2 full of glaze, is then brought into
contact with the surface to be decorated 11 of the tile 10 and pressed against it
undraggingly - this can be achieved, for example, by rolling the matrix, which could
be mounted on a cylinder, on the surface 11 of the tile 10 - with the elastic deformability
of the matrix causing the dosed amounts of glaze contained in the cavities 2 to
be expelled and transferred on to the surface 11 of the tile 10. The transfer of
the dosed amounts of glaze is facilitated by the fact that the surfaces delimiting
the cavities 2 are waterproofed and free of undercuts. The use of the matrix obtained
using the process of the invention is preferably accompanied by the use of a doctor
to scrape away the extra glaze from the smooth external surface 7 of the matrix
so that the glaze fills only the cavities 2 while the surface 7 is left perfectly
The invention has, among others, the not inconsiderable advantage
of enabling engraved matrices to be made using a traditional and economical silk
screen manufacturing technique.