The present invnetion relates to a transfer printing process
employing a particular composite which can be used in the bag tecnique, as described
hereafter, to obtain a drawing reproduction wuth a very good picture definition,
very good chromatic yield and substantially defect free, such as bubbles, dots,
More specifically in the transfer printing of the invention
the colour transfer is made by sublimation and a particular composite film is used
comprising a mated polymer film having a metallized surface on which a drawing,
preferably coloured, is printed.
More in particular said process is applied to flat surfaces
and tridimensional articles and is carried out under reduced pressure, optionally
by treating the composite, before the printing, with conventional techniques so
that the composite results electrostatically charged.
Still more in particular the process of the present invention
uses a composite comprising a basic polymer film having one or both the surfaces
mated, i.e., opaque and rough, wherein a mated surface is metallized and on the
metal layer a drawing, preferably coloured, is printed by sublimable inks at the
temperatures of the transfer printing process.
The transfer printing is a consolidated and diffused printing
technique in the industries of this field.
Compared with the conventional printing, the transfer printing
shows the following advantages:
- more faithful reproduction also of high complexity drawings (four-colour process);
- lower printing costs, since less sophisticated colour transfer plants are required;
- reduced environmental impact, the total amount of colours dispersed in the environment
being very low;
- as regards the printing on textiles, elimination of the vaporization, washing
and finishing phases used in the conventional printing, and therefore elimination
also of the respective processing recycling.
By using the transfer printing technique the drawing is
first printed, for example by rotogravure printing, on a suitable support; subsequently
the drawing transfer is carried out on the manufactured article, for example by
calendering for textiles or by heating in an oven for aluminum profiles or articles
of various shapes, at temperatures in the range 170°C -240°C. At said
temperatures the transfer step is complited in some minutes.
In European patent application EP 921,014 in the name of
the Applicant, a composite for transfer printing is described, formed by a basis
polymer layer on which a thin aluminum layer is deposited. On the aluminum surface
the drawing is printed by sublimable colours.
The composite can be used to print flat surfaces or tridimensional
articles such as aluminum profiles, doors and windows or others. In the patent application
it is described that in the tridimensional article printing the so called "membrane"
technique can be used, consistsing in coating the article wrapped in the composite
in an external membrane. Inside the pocket formed by the membrane, hermetically
sealed, vacuum is made. With this printing technique of tridimensional articles,
using the above described composite, printed manufactured articles are obtained
having a very good chromatic yield and definition of the transferred drawing.
Another technique to print tridimensional articles with
drawings having sublimable colours is the so called "bag" technique. Said technique
is industrially cheaper than the "membrane" technique, since the printing preparation
steps are simpler and the whole cycle is carried out in shorter times. The external
pocket, which constitutes the bag, is formed in this case by the same composite
film. During the printing step the vacuum is kept by connecting the pocket to a
The Applicant has found that the transfer printing by the
bag technique on tridimensional articles and non, carried out by the composite of
the above European patent application, has a lower quality in comparison with the
printing obtained in the same conditions by the membrane technique. See the Examples.
The need was therefore felt to have available a transfer
printing process by colour sublimation on tridimensional articles and flat surfaces,
carried out by means of the bag technology as above defined, such to allow to obtain
a manufactured article having the following property combination:
- defect free (bubbles, blurrings in the printed drawing, etc.),
- very good imagine definition and chromatic yield comparable with that obtainable
by the membrane transfer printing technique by using the composite of the above
European patent application,
- easy transfer with high definition of complex drawings, such for example the
drawing of the pinewood grain.
The Applicant has surprisingly and unexpectedly found a
process wherein the bag transfer printing technology is used which solves said technical
An object of the present invention is a transfer printing
process by colour sublimation by means of the bag technology, comprising the following
- a) coating of the article surface to be printed with a composite comprising:
characterized by a gloss < 60%, determined by the DIN 67530 method with measurement
angle of 85°;
- a polymer film or sheet, which forms the composite basis and is capable to resist
without decomposing and without being deformed at the temperatures used in the colour
transfer phase by sublimation, said polymer film or sheet having a thickness ranging
from 6 to 100 µm and having one or both the surfaces mated, therefore rough
- an aluminum layer, having a thickness fromt 0,5 to 40 nm preferably from 1 to
20 nm preferably having an optical density in the range 0.05-3.0, preferably 0.1-0.5,
measured by TD 932 - Macbeth densitometer, the aluminum layer being deposited on
a mated surface of the polymer compound film;
- a drawing, with the respective colours, printed on the aluminum layer and put
into contact with the surface of the article to be printed;
- b) longitudinal closing of the case formed by the composite and vacuum application
or pressure reduction between the composite film and the article to be printed,
using a residual pressure from 0.05 bar (5X103 Pa) to 0.2 bar (2X105
Pa), preferably 0.1 bar (104 Pa);
- c) heating at temperatures from 170°C to 240°C, preferably from 190°C
to 210°C, keeping the residual pressure within the previous limits, for a time
from 1 minute to 5 minutes;
- d) cooling and recovery of the printed article.
The longitudinal closing of the case formed by the composite
can be carried out for example by adhesive tape, or by ultrasound welding, using
The vacuum is applied to the two ends of the case formed
by the composite by a pump.
Optionally, the composite can be treated by conventional
techniques so that it results electrostatically charged when used in the process
according to the present invention. In this way the adhesion of the composite to
the article is easier and therefore the bag formation and the vacuum application
To carry out the printing process, for example an oven
suitable to this purpose or any other equivalent equipment can be used.
The thickness of the polymer compound film is preferably
from 10 to 25 micron and the optical density of the aluminum film, determined as
above, is preferably from 0.1 to 0.5.
Preferably the gloss of the rough surface of the polymer
film forming the basis composite film, is > 10%, measured by the above method,
but with contact angle of 60°, still more preferably it ranges from 15%, measured
with angle of 60° to 55%, measured with angle of 85°, extremes included.
The polymer forming the film or sheet is selected from
polyesters, fluorinated resins, polyamides, polyimides, polyethers and polyurethane
Preferably a polymer film of polyester, in particularl
polyethylene terephthalate, polybutylene terephthalate, glycol terephthalate is
Also polymer films stretched in one or both the directions,
longitudinal and/or transversal, can be used.
The results obtained with the composite of the present
invention are surprising since tests carried out by the Applicant have shown that
by using only the basis polymer film, with the mated surface, the transferred imagine
definition and the chromatic yield are not satisfactory.
Furthermore the use of the composite of the present invention
allows a significant time reduction of the transfer printing process, contemporaneously
using lower temperatures and lower times with respect to non metallized mated films.
The preparation process of the composite film used in the
process of the present invention takes place in two steps.
In the first step the mated polymer film is prepared.
This step can be carried out according to known methods,
for example by extrusion of the polymer containing inorganic fillers, or by chemically
or mechanically treating, for example by embossing or by applying a resin layer
on one or both the film surfaces, or by the "crown" treatment using well known methods
to the skilled man in this field.
Mated polymer films are easily available both by the plastic
compound manufacturers and on the market.
The mated films are indeed largely used for the flexible
The metallization of the mated surface of the polymer film
is carried out by deposition of an aluminum layer under high vacuum conditions,
using the usual techniques well known to the skilled man in this field.
The film is printed with the drawing to be transferred
on the side coated with aluminum, by using offset, flexo, rotogravure, serigraphy
printing machines, preferably a rotogravure printing machine is used.
The used inks are those usually available on the market
and that can be emulsifiable or disperseable in water or in solvent and must preferably
be of the type having high resistance to light.
With the composite film according to the present invention
both flat surfaces and tridimensional articles, even with irregular surfaces, can
As said, the colour transfer on the final support according
to the process of the present invention is carried out by the colour sublimation
technique at temperatures preferably from 190°C to 210°C.
The contact time is generally from 1 minute to 5 minutes,
and varies depending on the article mass and on the thermal exchange process conditions
during the transfer step.
The transferred colour amount is of the order of 90% or
As said, in the printing of tridimensional articles or
flat surfaces, the image definition results comparable with that obtained by using
the metallized composite of the prior art in the membrane transfer printing technique
Generally the invention films can be used for the transfer
printing by applying them to any article to be printed formed by a compound resistant
to the temperatures used in the printing process by sublimation and having surfaces
capable to absorb the sublimable colours which are transferred from the metallized
According to a preferred embodiment of the present invention
process the surfaces of the support to be printed are previously coated, for example
by electrostatic painting, with a layer of polymer compound, for example polyester
or polyurethane thermosetting powders, formulated so to favour the sublimable ink
The composite films of the present invention can be used
for the transfer printing technique for the application to supports formed by different
materials, for example metals (aluminum, iron, zinc, steel, cast iron), or glass,
ceramic, or polymer compound manufactured articles.
The materials can have the form of both flat surfaces and
It has been found by the Applicant that by using the invention
composite at the temperatures used in the transfer printing process, the drawing
does not result deformed when it is printed on the manufactured article. This represents
a remarkable advantage since the articles to be discarded for said printing defect
are practically absent.
The process according to the present invention is much
more unexpected if one considers that the use of the only mated film in the transfer
printing by colour sublimation does not allow to obtain a very good imagine definition.
See the comparative Examples.
Another object of the present invention is the composite
used in the printing process which has been described above.
The following Examples have the purpose to illustrate the
invention and are not to be intended as limitative of the scope of the same.
EXAMPLE 1 (comparative)
Use of the composite according to the European patent application
EP 921,014 in the transfer printing by means of the bag technology
An unmated polyethyelenterephthalate film (gloss = 100%)
having a thickness of 23 µm metallized on one side with aluminum having a thickness
of 12,5 nm, corresponding to an optical density determined by densitometry of 2.1
(metallized film A) is printed with a colour drawing reproducing the pinewood grain.
The receiving support is an aluminum profile for door and
windows, having sizes of about 7 meters x 10 cm x 5 cm, pretreated by electrostatic
painting with polyester thermosetting powdered paint having a thickness of 75 micron.
The composite film is wrapped around the profile, so that
folds do not form, and hermetically sealed on the longest side. By a pump a vacuum
of 0.1 bar (104 Pa) is made, taking care that folds or bubbles between
the composite and the article do not form. The transfer printing is effected by
transferring the wrapping wrapped on the aluminum profile in an oven at 205°C
for 4 minutes, keeping the vacuum at the above indicated value by means of the pump.
At the end it is cooled, the atmospheric pressure is restored
and the composite film is taken away from the article.
The drawing printed on the aluminum bar (Fig. 1) shows
printing defects attributable to air bubbles or non evacuated vapors, which have
prevented the film from contacting the paint layer on the profile. Besides, some
particulars of the printed grains result blurred. Therefore the reproduction of
the printed drawing is not good. It is observed that on the used composite only
traces of the sublimable inks remain. Therefore the colour transfer on the aluminum
bar has been substantially quantitative.
Transfer printing by the bag technology using a composite
wherein the basis polymer film surface is mated and has a gloss of 45%
Example 1 is repeated but by using a composite film in
which one of the basis film surfaces is mated and then it has been metallized with
The mated surface has a gloss of 45% determined by the
DIN 67530 method, by using a measurement angle of 85°.
The drawing printed on the aluminum bar (Fig. 2) does not
show defects (no air bubbles or blurrings) and it is of a very good quality. It
is observed that on the used composite only traces of the sublimable inks remain.
Therefore the colour transfer on the aluminum bar has been substantially quantitative.
If Figures 1 and 2 are compared, one clearly sees that
the drawing reproduction in the case of Figure 2 is evidently higher than that obtained
in Figure 1.
EXAMPLE 3 (comparative)
Printing with the bag technology using only the mated basis
Example 2 is repeated but by using only the mated basis
polymer film (not metallized with the aluminum layer) on which the same colour drawing
The drawing printed on the aluminum profile (Figure 3)
in this case shows a lower definition than that obtained in Example 2. At the visual
observation it is noticed that the lines reproducing the grains are discontinuous,
mostly formed by a sequence of points: the drawing shows the printing defect known
as "uncompactness" and it is not of an acceptable quality.
It is noticed that on the polymer film recovered at the
end of the process an evident amount of inks remains, such that the original drawing
is easily recognizable. Therefore by using only the mated polymer film in the transfer
printing process with the above mentioned technique, the colours are only partially
transferred to the support.
Transfer printing by the bag technology by using a composite
in which the basis polymer film surface is mated with a gloss of 20%.
One proceeds as in Example 1 but by using a composite film
wherein one of the basic film surfaces is mated and has then been metallized with
The mated surface has a 20% gloss, determined by the DIN
67530 method, by using a measurement angle of 60°.
The drawing printed on the aluminum bar (Fig. 4) does not
The definition of the printed drawing results slightly
lower than that obtained in Example 2.
On the whole the obtained print results of good quality
and it is therefore acceptable.