EP4603295A1

EP4603295A1 - Procedure for making transfers via an optimised printer

Info

Publication number: EP4603295A1
Application number: EP25155990.2A
Authority: EP
Inventors: Stefano SCALDAFERRO
Original assignee: Multi Griffe Srl
Current assignee: Multi Griffe Srl
Priority date: 2024-02-15
Filing date: 2025-02-05
Publication date: 2025-08-20

Abstract

The Invention describes an optimisation of the technique to create graphical elements known as transfers, which enables the elimination of steps to apply pounce adhesive and the use of particularly high temperatures to activate the adhesive element of transfers. The Invention also describes the optimisation of printing equipment to make transfers.

Description

Field of the Invention

This Invention describes a printing technique used to decorate a large variety of surfaces, such as fabric, clothing, footwear, plastic, fashion accessories etc., especially when featuring special colour effects, even at high resolution, applied using a graphical element known as a transfer.

Background to the Invention

Printing techniques have evolved through the acceleration of technology in recent decades, resulting from the use of digital processes.
Printing processes have changed on the basis of significant factors that can be summarised as follows:

a. the print quality required, in terms of resolution and colour detail,
b. the print medium,
c. the resilience of the graphical elements applied with the printing process.

Excluding printing processes on paper, which do not represent this Invention's field of application, some older techniques are still widely used in industry, in which considerable experience has been acquired using highly reliable equipment.
One of these techniques in the Prior Art is screen printing, which consists of a fine mesh screen over a frame which is applied to the surface to be decorated. Colour is distributed using a self-propelled spatula on the upper surface of the screen i.e. the surface not in contact with the item to be decorated, which migrates to the underlying surface in the areas where the screen printing frame is positioned with appropriate micro apertures. The colour passing to the lower surface of the frame brings the colour into contact with the element to be decorated.
The screen printing technique can be repeated, changing the screen frames, to apply several colours to the same surface, and the series of printing processes will create the final effect of the graphics.
Screen printing optimisations are currently available which also enable printing on complex surfaces, provided they can be placed tangentially to a screen printing frame, even for example by moving it in synchrony with the item to be decorated.
There are various types of screen printing machines currently on the market. These range from manually operated machines which cost a few hundred euros to complex, industrial-scale equipment that is Industry 4.0 compliant, fully automated and with a high-speed printing process, mainly used for industrial production operations.
An example of the versatility of screen printing is given in US patent US11491777B2 , in which a screen printing machine enables several areas of a garment to be printed, such as a shirt, using numerous screen printing frames.
However the main disadvantage of the screen printing technique is that it cannot print on uneven or irregular surfaces that are rigid or semi-rigid, and which cannot be placed tangentially to the whole surface of the screen printing frame. Furthermore, screen printing requires the items being decorated to be suitably prepared, as illustrated in US11491777B2 , such that they can be optimally positioned in contact with the screen printing frame.
Another technique for decorating surfaces that is widely used is pad printing, involving a printing plate with a negative 3D relief design representing the silhouette of the required graphical element. An ink roller distributes a liquid colour over the plate, which is positioned in contact with the surface of an elastic silicone pad. The colour distributed on the printing plate is transferred to the silicone pad, which is then applied to the surface to be decorated and carries out the printing process.
Pad printing is carried out with smaller equipment than screen printing machinery and has a major advantage in that it can decorate surfaces that are not perfectly flat. The use of an elastic silicone pad also enables adhesion on uneven surfaces and relief designs by applying suitable pressure to the pad.
Pad printing is used in the Prior Art to decorate a variety of items, including small objects such as the temples on spectacle frames, alphanumerical characters on computer keyboards and various types of mechanical components. Pad printing is therefore an extremely versatile technique, as illustrated in US patent US11358382B2 , in which a particular-looking pad is used to decorate the curved surface of an electronic device display.
US publication US2002174783A1 also describes the versatility of optimised pad printing to print graphical characters on a computer keyboard.
However even though a silicone pad features intrinsic flexibility, there may be areas of application where the aforementioned pad printing cannot be used satisfactorily. This depends on the shape of the item to be decorated and its constituent materials, which may not be fully compatible with inks and adhesives applied using pad printing.
A solution available on the market for printing on very complex or irregular surfaces is the use of transfers i.e. adhesive graphical elements, therefore with glue, specially made on sheets of flexible backing e.g. plastic, which are applied to a surface to be decorated. Once applied, the backing is removed while the graphic sticks to the surface being decorated, thanks to its own adhesive.
This technique obviously overcomes the limitations of the previously mentioned screen printing and pad printing techniques, as the sheet of backing which contains the adhesive colour is extremely flexible and can adapt to any type of surface.
In spite of these advantages, transfers have room for improvement. The adhesives used for applying colours when using transfers must also be suitably formulated for the bases upon which they are acting, and the composition or implementation of colours to be applied could be incompatible with the transfer creation processes.
In Italian application IT102021000013514 for example, the transfer is made in two phases. In the first only the adhesive element is applied to the surface to be decorated by means of the backing, and a second step releases the colour onto it from a sheet of pigment, which adheres to the previously mentioned adhesive element. The transfer is therefore the coloured element on its backing.
The technique described in IT102021000013514 therefore has two advantages:

a. the first is the selection of an adhesive applied to the backing that is suitable for the material on which it is acting,
b. the second is that the colour from the sheet of pigment applied to the adhesive may contain features that cannot be reproduced or implemented with printing, such as glitter or visual chromatic/mirror effects.

Recent developments in printing have resulted in a new process for creating transfers called Direct To Foil (DTF), whereby the required graphics are printed on flexible transfer backing by means of inkjet printers. DTF printers therefore have tanks and nozzles in the print heads to dispense the colours that make up the decoration applicable with the transfer, whereby the decoration is created by the aforementioned DTF method on a suitable backing made of synthetic material.
The basic steps for making transfers using the DTF technique are as follows:

a. a sheet of backing is placed in a DTF printer which creates the desired graphical element i.e. decoration, complete with its colours,
b. the backing is removed from the printer and undergoes a process to distribute adhesive on the decoration created previously; this adhesive is applied in powder form and released through gravity via equipment or manually,
c. the sheet of backing is heated to cure the adhesive, using an oven set to a temperature of between 85 and 160 degrees Celsius,
d. The backing bearing the graphical element is applied to the surface to be decorated, such as a fabric, using a press or flexible pad, or any other technique in the Prior Art for applying transfers,
e. the backing is removed from the graphical element, which now adheres to the surface undergoing the transfer printing technique.

The advantage of this process is being able to achieve all colour levels required by the graphics automatically with a printer. The operation is quickly implemented by the printer and fully reproducible by users when equipped with specific software to process these graphics.
Another benefit of creating transfers via a printer is the low cost of this equipment, as by and large it has derived from inkjet printing techniques used for printing on paper.
DTF printing optimises what are known as Direct To Garment (DTG) printing processes where surfaces to be decorated, such as a top or fabric, are loaded into a DTG printer in which ink jets act directly on the surfaces of the top or fabric. This printing process is extremely fast because it operates directly on the surface, however there are three significant disadvantages:

a. the high cost of DTG printers,
b. as with screen printing, it must be possible to stretch the surface being decorated perfectly, so that the printer heads can operate on it properly. To do this the printer has a dedicated tractor unit that stretches the fabric out, and heat is also used.
c. The surface to be decorated must be pre-treated with specially-designed chemical solutions.

An analysis of printing techniques in the Prior Art shows that the transfer technique by means of a printer undoubtedly has the most benefits, as it is built around an automatic inkjet printing process and enables users to obtain printing equipment at a relatively affordable cost.
However this technique has two limitations - the process for applying adhesive on the graphics produced with this printer involves an operation that is separate to the transfer creation step. Furthermore, the adhesive must be suitably heated to high temperatures of even greater than 100 degrees Celsius to be able to act satisfactorily. In general, DTF printing processes can be considered within inkjet technology, where the DTF method is a specific application.
The aim of this Invention is to improve the transfer element in the Prior Art through inkjet and/or DTF printing processes, and to create ready-to-use transfers via an optimised printer, without the need for another step to distribute pounce adhesive on the transfers. Another aim of this Invention is to limit the peak temperature required to activate the adhesive added to the transfer graphics.

Summary of the Invention

Benefits of the Invention

This Invention offers the following advantages:

a. as per the process in this Invention, the transfer element is created using an automatic printing process, including the DTF type, complete in its entirety, so it can be applied immediately to the surface to be decorated without having to apply a pounce adhesive as in processes in the Prior Art,
b. as per the process in this Invention, the transfer element can be heated at moderate temperatures instead of high temperatures - at around 40-50 degrees Celsius - using non-professional, non-specialist equipment, thereby also saving energy and time in the production process,
c. as per the process in this Invention, the transfer element is produced using a process that is simpler than current processes in the Prior Art.

Description of Diagrams

A table with diagrams is included with the documentation for this application to illustrate the characteristics of the invention, with application variations highlighted where described. More specifically it includes:

Fig.1
[fig.1] showing an exploded view of the layers forming the transfer, as per the procedure in this Invention,
Fig.2
[fig.2] showing the construction sequence in an exploded view of the transfer, as per the procedure in this Invention,
Fig.3
[fig.3] showing the last layer called the 'shield', as per the procedure in this Invention,
Fig.4
[fig.4] showing the construction sequence in an exploded view of the transfer, including the shield as per the procedure in this Invention,
Fig.5
[fig.5] showing a DTF and/or inkjet printer in the Prior Art,
Fig.6
[fig.6] showing print heads in the Prior Art on an inkjet printer, including the DTF type,
Fig.7
[fig.7] showing the heads of a printer optimised as per the procedure in this Invention.

Description of the Invention

The description of the various methods for implementing this Invention is outlined for illustration purposes, therefore all possible modifications of an obvious nature in its field of application, when carried out by industry operators, will not limit the terms for protecting the licence itself. Furthermore, in the wording of this Description, the definition of 'printing process' is to be understood as the process by which inkjet and/or DTF printing enables the creation of a graphical element on a sheet of backing, and the graphical element can then be transferred to the surface of an item.
As per the Invention implementation method, the transfer is implemented using flexible backing in a synthetic material (10), preferably polypropylene, polyester or polyurethane, made in the form of a thin sheet of between 80 µm and 200 µm in thickness, as required. In Fig.1 the thickness of the backing (10) is shown in a diagram that is not to scale, in order to illustrate the transfer implementation technique clearly.
As per the Invention implementation method, the flexible backing can be constructed in individual elements i.e. all separate from one another with several sheets, or in one continuous unit, enabling it to be wound into reels. In both cases the backing is conveniently stuck to protective paper. This enables one of its surfaces to be protected, that which is to be decorated by the printer, including the DTF type. It also keeps the backing stretched out and facilitates loading into the aforementioned printer.
As per the Invention implementation method, the backing is the base upon which the printer deposits all subsequent layers of graphics and features that form the fully-fledged graphical element and enable it to be transferred to the surface to be decorated. The thickness of the backing, already stated in paragraph 0040, will therefore be compatible with the tractor unit in the aforementioned printers, to be able to feed it in correctly.
As per the Invention implementation method therefore, the flexible backing is the element in the Invention that can be removed once the surface decoration process is complete. The flexible backing is not actually part of the decorative feature achieved with the printing process, it is just a temporary element on which the graphics are created using the printer and enables its application.
As per the Invention implementation method, the transfer has four main overlapping layers, one of which is the flexible backing (10).
As per the Invention implementation method, an optional fifth layer can be added, and this could also form part of the idea of the Invention.
In Fig. 1 each layer is shown as a well-defined rectangular area, however the layers could be of a different shape, even made up of solely colour and/or adhesive elements, such as a coloured graphical element, as shown in (13). Therefore in the wording of this Description, the layer identifies the concept of overlapping steps as per the idea of the Invention; the flexible backing however will always have its own physical characteristics determined by its constituent synthetic material, as stated in 0040.
As per the Invention implementation method, a second layer known as a release layer is created. This layer is required as the decorative element, which will be created with the subsequent layers deposited by the printer, must detach from the backing easily during the process to apply the transfer to the surface being decorated. Therefore the release layer facilitates the removal of the flexible backing from the graphical element of the transfer.
In the Prior Art the release step is already used in transfer techniques and is carried out using an embossed roller or similar technique, and involves synthetic resins or derivatives of natural substances such as wax. When of synthetic origin they can be made with particular cross-linking characteristics activated by various factors, such as UV rays, as outlined in Application IT102021000013514 ( IT102021000013514 , Description, paragraph 0019).
As per the Invention implementation method, and unlike the Prior Art, a release (11) treatment is developed that is applied via the printer, which is optimised in this Invention by positioning another tank and another print head, with which this release treatment is applied automatically on the flexible backing. To do this the viscosity of the release is modified with respect to that which is known in the Prior Art, to enable it to be dispensed through the print head of the aforementioned optimised printer, including the DTF type. The release therefore has a viscosity of between 4000mPa and 6000 mPa. The release treatment can also be designed to activate, via crosslinking, when exposed to UV rays, to enable the final decorative layers to be applied to the surface.
As per the Invention implementation method, this automated application of the release treatment via the optimised printer saves considerable time in producing the Invention i.e. the transfer, as it consists of a fully automated process.
As per the Invention implementation method, the third layer is then created, which represents the actual graphical element of the decoration, called the graphics layer. The graphics layer is created by the action of the colour print heads on the optimised printer, which has already-known separate tanks for the base CMYK colours (cyan, magenta, yellow and key black), and an optional tank for W (white) used for applications on particular plastic surfaces, such as polypropylene or ABS. Water-based resin inks are used, which have been specially formulated for use with the aforementioned printers. They are already known in the Prior Art and have been created to adhere to various materials to be decorated.
As per the Invention implementation method, the graphics layer (12) is created over the release layer and can have a shape and colour in line with customer requirements, by programming the optimised printer using graphics editing software in a connected hardware device.
As the graphics layer is created over the release layer on the flexible backing, the graphical element of the transfer must be printed in reverse i.e. turned over horizontally (13), so that when being applied to the surface being decorated it is turned over and in the correct position for being read or interpreted.
As per the Invention implementation method, once the graphics layer of the transfer has been created, a specific coating representing the fourth layer (14) is applied. The fourth layer is also applied using the optimised ink jet printer, which is set up with an additional tank and print head for the substance constituting the fourth layer in this Invention.
As per the Invention implementation method, the fourth layer is called the adhesive layer and is made of a thermoplastic resin. The thermoplastic resin fully replaces the pounce adhesive application subsequent to the printing typical of the Prior Art, thereby avoiding this additional process carried out manually or using specific equipment, as illustrated in the non-patent literature shown at https://www.youtube.com/watch?v=Fqpk4VgVhr0
As per the Invention implementation method, the thermoplastic formulation of the adhesive layer is created with a specific viscosity so it can be dispensed through its print head on the optimised DTF printer in this Invention. The adhesive layer therefore has a viscosity of between 4000mPa and 6000 mPa. Surprisingly, the viscosity of the adhesive layer enables it to be activated using heat at a temperature range that is much lower than that of the pounce adhesive process in the Prior Art, resulting in a significant procedural benefit.
Therefore as per the Invention implementation method, the complete transfer element is made according to the sequence of layers shown in Fig.2, starting with the flexible backing (20) which is fed onto the tractor unit of the optimised printer, even a DTF type i.e.:

a. the release layer (21),
b. the graphics layer (22),
c. the adhesive layer in thermoplastic material (23).

As per another Invention implementation method, and as outlined in paragraph 0045, another transparent layer called the shield or protective layer can be applied to the transfer element. The shield is created to protect and preserve the graphical element of the transfer by means of a specific layer of a chemical substance.
As per the Invention implementation method, the shield is made of:

a. a transparent acrylic formulation if the transfer is to be applied to a plastic surface,
b. a transparent polyurethane formulation if the transfer is to be applied to a natural fabric surface,
c. in both formulations the shield is of a viscosity that is compatible with the heads and jets of the optimised printer in this Invention. The shield is therefore created with a viscosity of between 4000mPa and 6000 mPa.

As per the Invention implementation method and as outlined in the previous paragraph, the shield is also applied using the optimised printer, which is set up with a dedicated tank and print head.
Fig. 3 shows an exploded view of the 5 layers making up the transfer in this Invention, clearly illustrating the shield layer (30), whereas Fig. 4 shows the exact implementation sequence for the transfer element in this Invention, starting with the flexible backing (40) fed onto the tractor unit of the optimised DTF printer i.e.:

a. the release layer (41),
b. the shield layer (42),
c. the graphics layer (43),
d. the adhesive layer in thermoplastic material (44).

The technique in the Prior Art relating to the construction of printers, including the DTF type (50), requires several print heads on the same machine, enabling them to apply more than one colour at a time in one print operation, as the heads are aligned vertically. This feature makes it possible to create the entire graphical element of the transfer with one print operation. It should be noted that the printing process can also be carried out by large print stations where the equipment does not resemble that which is considered to be a typical printer - these are dedicated industrial systems. Even though the external appearance of a printer can vary, the aim of this Invention is to claim the functions of the aforementioned machinery when optimised with the idea of the Invention, as specified in Claim number 7.
Fig. 6 shows the typical layout of two print heads (60, 61) operating in sequence, each of them handling a different colour (62, 63) obtained from the respective tank (64, 65), thereby depositing the two colours required by graphics on the backing (66) with one printing process. Fig. 6 also shows the horizontal movement of these print heads (67) from above, once again on the flexible backing (68).
As per the Invention implementation method, a printer in the Prior Art is therefore modified with the addition of a further three separate tanks and associated print heads, to conveniently apply the following in one process:

a. the release layer,
b. the shield layer,
c. the thermoplastic adhesive layer.

As described in paragraph 0064, Fig. 7 shows the complete layout of the heads on the optimised printer in this Invention, in which groups of heads for the colours CMYK and W (72) are shown in one group for convenience.
The first tank/head group in Fig. 7 handles the release layer (70), the second group handles the shield layer (71), the third group the colour layer of the transfer CMYK and W (72), and the fourth group the thermoplastic adhesive layer (73), with all groups operating on the flexible backing (74).
As per the Invention implementation method and as described in previous paragraphs, the formulation of the thermoplastic adhesive applied with the printer removes the need for its external application using pounce adhesive, thereby also avoiding the corresponding heat process with temperatures even in excess of 100 degrees Celsius.
As per the Invention implementation method, the thermoplastic adhesive layer applied to the transfer is actually activated before the transfer application process without using any specific oven, solely by bringing it to a temperature of between 50 and 60 degrees for between 120 and 240 seconds on average. This activation characteristic is due to the thermoplastic nature of the adhesive in this Invention.
As per the Invention implementation method, this heating process can easily be implemented with a flow of warm air generated by a heat gun or a preheated chamber, also saving energy in the transfer production process due to the considerable difference in temperature required to activate the thermoplastic adhesive compared with the pounce adhesive in the Prior Art.

Invention examples

None

Industrial Applications of the Invention

This Invention is applicable to industry in large-scale printing operations or craft technical transfer processes.

Citations in the Invention

Citation List follows: none.

Patent Literature

PTL1: US11491777B2
PTL2: US11358382B2
PTL3: US2002174783A1
PTL4: IT102021000013514

Non-Patent Literature

NPL1: https://www.youtube.com/watch?v=Fqpk4VgVhr0

Claims

[Process for the realization of transfer-type graphic element for the decoration of synthetic or natural surfaces, obtained with a plurality of processes put in place by a printer, also of the inkjet type or DTF (Digital To File) type, on a flexible support of synthetic material, in which:
a. the flexible support (10, 40) is realized in Polypropylene, Polyester or Polyurethane, said support characterized by a thickness between 80µm and 200µm,

b. the flexible support feeds the tractor of a printer (50),

c. the printer prints the following layers on the flexible support:
i. a release substance layer (41), said release consists of a synthetic resin based, capable of cross-linking through exposure to Ultraviolet rays, said release formulated with a viscosity between 4000 mPa and 6000 mPa,

ii. a graphic layer (43) applied on the release layer, consisting of the combination of the CYMK basic colours (Cyan, Yellow, Magenta, Key Black) and an optional additional colour W (White), these colours formulated with a water-based resin,

iii. an adhesive substance layer (44) applied on the graphic layer, said adhesive layer consisting of an adhesive thermoplastic resin; said adhesive layer formulated with a viscosity between 4000 mPa and 6000 mpA.
Process of Claim 1 in which, upon the release layer and before the graphic layer, the printer realizes a substance layer called shield (42), said shield formulated with a viscosity between 4000 mPa and 6000 mPa, said shield layer consisting of:
a. a transparent acrylic formulation if the transfer graphic element is applied on a plastic surface,

b. a transparent polyurethane formulation, if the transfer graphic element is applied on a natural textile surface.
Transfer element obtained by the procedure of Claim 1 consisting of:
a. A flexible support (10, 40) realized in Polypropylene, Polyester or Polyurethane, said support characterized by a thickness between 80µm and 200µm,

b. a release material layer applied on the flexible support, said release consisting of a synthetic resin able to cross-link through exposure to ultraviolet rays, said release layer applied by a printer,

c. a graphic layer applied on the release layer consisting of the combination of the CYMK (Cyan, Yellow, Magenta, Key Black) basic colours and an optional additional colour W (White), said colours formulated with a water-based resin, said graphic layer applied by a printer,

d. an adhesive layer applied on the graphic layer, said adhesive layer consisting of an adhesive thermoplastic resin, said adesive layer applied by a printer,
Transfer element of Claim 3 in which, on the release layer and before the graphic layer, is applied using a printer a layer of a substance called shield, said shield layer consisting of:
a. a transparent acrylic formulation if the transfer graphic element is applied on a plastic surface,

b. a transparent polyurethane formulation if the transfer graphic element is applied on a natural textile surface,

c. the shield layer is formulated with an viscosity between 4000 mPa and 6000 mPa.
Transfer element of Claim 3 and 4 realized on a single flexible support sheet.
Transfer element of Claim 3 and 4 realized on continuous flexible support sheet wrapped on spool.
Inkjet or DTF (Digital To File) printer, for printing transfer-type graphic elements of Claim 3 and 4 by the procedure of Claim 1, including:
a. a reservoir and a print head for the distribution of the release substance (70), said release consisting of a synthetic resin capable of cross-linking through exposure to ultraviolet rays and formulated with a viscosity between 4000 mPa and 6000 mPa,

b. a reservoir and a print head for dispersing a substance called shield, said shield formulated with a viscosity between 4000 mPa and 6000 mPa, said shield consisting of:
i. a transparent acrylic formulation if the transfer graphic element is applied on a plastic surface,

ii. a transparent polyurethane formulation if the transfer graphic element is applied on a natural textile surface,

iii. reservoirs and their print heads for dispersing a basic combination of the CYMK colours (Cyan, Yellow, Magenta, Key Black) and an optional additional colour W (White), said colours formulated with a water-based resin,

iv. a reservoir and a print head for dispersing an adhesive (73) consisting of an adhesive thermoplastic resin, said adhesive formulated with a viscosity between 4000 mPa and 6000 mPa.
Transfer element of Claim 3 and 4 in which the thermoplastic adhesive is activated by heating to a temperature between 50 and 60 degrees Celsius for a time between 120 seconds and 240 seconds.