CH719596B1 - Process for drying a layer of conductive ink on a polymeric layer of a flexible multilayer structure. - Google Patents

Abstract

The invention relates to a method for drying a layer of conductive ink during the manufacture of a flexible, planar, multilayer structure (100) in film form, for example an electronic structure or an electrothermal structure, the method comprising deposition of a layer of conductive ink on a polymeric layer comprising said flexible multilayer structure, the conductive ink being a graphene ink, prepared by mixing graphene with resins and/or solvents, and drying the conductive ink layer, characterized in that said drying is done by infrared rays.

Description

TECHNICAL AREA

The present invention relates to a method for drying a layer of conductive ink on a polymeric layer during the manufacture of a flexible multilayer structure, said conductive ink being a graphene ink.

STATE OF THE TECHNIQUE

[0002] There are heating films comprising an electrothermal layer between two insulating layers. Flexible films comprising electronic components are also known, these films comprising electronic components such as resistors, capacitors, or RF antennas for example. Other flexible films can be used to make batteries. These films often use conductive ink, which must be dried before adding another layer, for example a layer of insulation. An aim of the present invention is to improve such a process, for example by making it faster, among other things.

SUMMARY OF THE INVENTION

[0003] An aim of the present invention is to define a method for drying a layer of conductive ink in the manufacture of flexible multilayer structures, for example electronic structures or electrothermal structures.

[0004] According to a first aspect, a method of drying a layer of conductive ink during the manufacture of such a flexible, planar multilayer structure, in the form of a film, is presented. The method comprises the following steps: depositing a layer of conductive ink on a polymeric layer which will comprise said flexible multilayer structure, the conductive ink being a graphene ink, prepared by mixing graphene with resins and/or solvents ; drying of the conductive ink layer; ; and drying the conductive ink layer; characterized in that said drying is done by exposing the conductive ink to infrared rays.

[0005] According to a second aspect, a flexible, planar multilayer electronic and electrothermal structure, in the form of a film, is presented, the structure comprising a deposition of a layer of conductive ink on a polymeric layer which said structure comprises, the conductive ink being a graphene ink, prepared by mixing graphene with resins and/or solvents, and dried according to said method.

SUMMARY DESCRIPTION OF THE DRAWINGS

[0006] The characteristics of the invention will appear more clearly on reading the description of several embodiments given solely by way of example, in no way limiting with reference to the schematic figure, in which: – Figure 1 shows the different layers present in an electrothermal structure.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for drying a conductive layer during the manufacture of a flexible multilayer electronic structure. The structure is substantially planar, preferably elongated, extending in two dimensions over a length and a width, the length preferably being several times greater than the width.

The structure is an electronic structure in the sense that it comprises electronic components or circuits, these circuits or components being either positioned or deposited, or printed by a screen printing process, for example. Depending on the required functionality, these circuits or components can be resistors, capacitors, diodes, chokes, transistors or sensors of different types, for example. The structure may include an electrothermal material to produce heat. The structure may include a conductive layer comprising conductive traces for bonding the components and/or the electrothermal elements together to make one or more electrical circuits. The multilayer structure can be used to make batteries. Such structures can be used to make photovoltaic films.

The electronic part of the flexible multilayer electronic structures is located on one or more layers between a substrate and a passivation, the substrate and the passivation being electrical insulators, for example a polymer. The passivation and the substrate may each comprise two layers of the polymer glued together. The structure is therefore airtight and watertight, electrically insulating and mechanically resistant against scratches and/or cuts.

The flexible polymer may be, for example, polyethylene terephthalate (PET). Other polymers are also possible, for example polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), soft PVC (PVC-P), polystyrene (PS), polycarbonate (PC) , polymethyl methacrylate (PMMA), polyoxymethylene (POM), polyethylene terephthalate (PET), polyester, co-polyester, polyetheretherketone (PEEK), polyamide, in particular polyamide 6 (PA6), polyamide 12 (PA12), polyamide 10, polyamide 610, polyamide 66, polyamide based on aliphatic and cycloaliphatic constituents such as in particular MACM 12 or amorphous co-polyamide, preferably based on PA12, or copolymers or mixtures of these.

[0011] The flexible multilayer electronic structures comprise a base and a cap. The hat includes an electrothermal layer and the base includes the conductive layer which may include electronics. The flexible multilayer electronic structures of the present invention can be produced on a manufacturing line. The electronic part can be printed on the passivation to make a base. The hat is then attached to a substrate, i.e. the base, using glue. Bonding can be achieved by an adhesive which acts with mechanical pressure, i.e. a "PSA" (pressure sensitive adhesive), a pressure sensitive adhesive. A PSA is a type of non-reactive adhesive which forms a bond when pressure is applied. is applied to bond the adhesive to a surface.

[0012] A passivation layer can be rolled out from a first main roller 210. Optionally this passivation layer can be rolled up on a second main roller 220. The passivation is preferably a polymer, as described above To promote good adhesion of the layers which will be applied to the passivation, this passivation can, optionally, be previously treated with plasma.

[0013] Depending on the type of electronic structure to be made, for example a heating film comprising an electrothermal layer, a photovoltaic layer or a battery, the structure comprises graphene. This layer can be produced by depositing a graphene ink. The ink is prepared by mixing graphene with resins and/or solvents

[0014] For an electrothermal ink, for example, the molecular structure of graphene is hexagonal in two dimensions. For a conductive ink, we can use microparticles, or even nanoparticles, of graphene. Graphene nanoparticles can have a size on the order of 1 nm to 100nm. According to one embodiment, the molecular shape of the nanoparticles can be graphene nanowires, for example.

A planetary mixer can be used to ensure good ink homogeneity without air bubbles.

[0016] A layer of previously mixed graphene ink is deposited on the passivation, preferably by a slot die process, while the passivation takes place under the head of the slot die. The thickness of this layer can be controlled by controlling the unwinding speed of the polymer. The ink can be stirred or mixed at the same time as it is pumped into the slot die head. The pump pressure can also be used to control the thickness of the graphene ink layer. For an electrothermal structure, the graphene does not go all the way to the edges in the width of the passivation.

[0017] The graphene ink layer is then dried, preferably by a near infrared (NIR) ray (short wave) drying process, which promotes rapid drying of the ink without damaging the polymer. Drying can be done in pulses. The inks dry at 120°C for around 10 minutes, which is much faster than other techniques without infrared rays, which can have speeds around 6 m/min for a 60m drying tunnel at 125 degrees for example. With infrared rays drying can take around one to two seconds over a distance of 0.5m or 1m.

[0018] A so-called “carrier” layer is applied to the passivation. This layer can be applied before, during or after the graphene ink layer. The carrier layer may be made of polymer material. The carrier layer can be unrolled by a first carrier roller 230 and rolled up by a second carrier roller 240. This layer can be PET which is prepared with a layer of PSA glue. Pressure can be applied to the carrier layer and passivation to make them stick together, for example with a pair of rollers in a roller spinner configuration.

[0019] The graphene layer is generally continuous on the passivation after the inking process described above. It is possible to divide this graphene layer into a plurality of graphene blocks, or other defined designs. To be able to create specific areas of inking on the passivation with defined designs, recesses are made in graphene. The recesses can be made with a drum punch system to separate predefined inking areas with cuts. The cuts are made in the graphene layer and the polymer layer, up to the carrier layer. By removing the carrier layer, the regions of graphene layers that have been cut or scrap remain stuck to the carrier and can be discarded. Otherwise, this operation can be carried out by laser cutting.

[0020] A second layer of passivation is applied with PSA glue.

[0021] To complete the cap, electrodes are placed. Optionally integrated circuits or sensors or RFID modules can be placed or printed on the hat, as well as electrical connections, to make the desired electronic circuit. The circuits, modules or sensors are placed in the places which have been hollowed out.

[0022] Finally, strips or ribbons of PSA glue are placed in part of each recess and along the passivation on the edges which are devoid of graphene. A PSA strip or adhesive tape can therefore be unrolled and attached to the passivation on both edges of the structure where there is no graphene. The adhesive tape can also be stuck in the hollow areas, for example pre-cut with the machine in “label” mode.

[0023] A substrate polymer layer can be prepared with integrated circuits or electrical components or sensors or antennas or RFID chip or other printed circuit, as well as electrodes for connecting the electronics and/or for connecting to the graphene. Like the passivation layer, it is possible to treat the substrate layer with plasma to improve the bonding of the other layers on top. On this substrate layer there can also be connectors, deposited or printed, for example to connect several structures together. The electrodes and connectors can be formed with a conductive ink as described above. This polymeric layer, the base, can be rolled out over the hat and the hat and the base glued together using the adhesive tapes previously positioned.

[0024] A second polymeric passivation layer, prepared with a layer of PSA glue, can be glued to the first passivation layer. Similarly, a second polymeric substrate layer, prepared with PSA glue, can be glued to the first substrate layer.

If the structure includes one or more RFID chips, a test step includes reading the RFID chip.

The structure can be cut into long pieces comprising a given number of graphene blocks.

Claims (2)

1. Method for drying a layer of conductive ink during the manufacture of a planar flexible multilayer structure (100), in the form of a film, for example an electronic structure or an electrothermal structure, the method comprising: depositing a layer of conductive ink on a polymeric layer which will comprise said flexible multilayer structure, the conductive ink, being a graphene ink, prepared by mixing graphene with resins and/or solvents; And drying of the conductive ink layer; characterized in that said drying is done by infrared rays. 2. Multilayer structure (100), flexible, planar, in the form of a film, for example an electronic structure or an electrothermal structure, comprising a deposition of a layer of conductive ink on a polymeric layer which comprises said structure, the ink conductive being a graphene ink, prepared by mixing graphene with resins and/or solvents, and dried according to the drying process according to claim 1.