ITTV20120142A1 - IMPROVED MATERIAL IN WHICH REALIZE CONDUCTOR CIRCUITS - Google Patents

Description

“IMPROVED MATERIAL IN WHICH TO MAKE CIRCUITS

CONDUCTORS "

DESCRIPTION

The invention refers to a compound material, eg. to be spread or sprayed on any surface, in which to create conductive circuits and / or generators of electric charges, in the form of a signal or current. The compound can be modified by a magnetic field to vary its electrical conductivity, in particular through a laser.

Wiring surfaces or systems is a costly and laborious operation. The length of the cables, their cost and weight often have a preponderant impact, sometimes to the point of advising against starting the work.

WO20 11 125037 instead teaches how to create - more advantageously - conductive tracks inside a volume of a material thanks to molecules that can be made conductive in a stable way by means of the energy locally supplied by a laser. In the natural unexcited state, the molecules are electrically non-conductive, and the laser can activate them in the infinitesimal volume in which it hits them.

The precision of the laser allows the tracing of three-dimensional or layered tracks in many levels within the volume of material. Currently, the position of the track traced is determined by controlling the power of a single laser beam or the collimation in the space of two beams.

Both laser systems have disadvantages.

The tracking accuracy in the first system strongly depends on the positioning and displacement accuracy of the laser source, and on the attenuation of the material crossed. The active point of the Laser is in fact the one having the right power transferred to the molecules, decreasing with the distance from the source.

The second system is expensive and complex, because it has to obtain and manage the collimation of two or more laser beams at a moving point.

It is therefore convenient to solve some of these problems, while maintaining a precise and reliable tracking system. In particular, it is desirable to have a less complex and expensive tracking system.

The solution is defined in the attached claims, i.e. in general - a material suitable for the realization within it of an electrically conductive track or area by means of laser tracing, characterized in that it comprises

- a dye or coloring particles to absorb a certain frequency of laser radiation.

It is then possible to trace tracks or areas in a volume of compound / material / substrate without using sophisticated and expensive laser techniques. A "colored" layer of the material will be sensitive, or more sensitive, to a particular laser wavelength, while the other areas will not.

Within the material, areas can be defined with a laser absorption frequency typical of the characteristic color of the dye or of the coloring particles contained therein. So eg. a green laser will operate on the green dye area, and so on. The power of the laser must be chosen experimentally or by exploiting the known knowledge on lasers and materials.

The frequency selectivity and spatial accuracy are improved by the dye in the material, allowing to mitigate the precision specifications on the Laser, the structure of which is simplified, e.g. to a single device, eg. portable, capable of generating different frequencies corresponding to the various colors of the dyes or particles added in the material.

A dye or dye particle can be chosen between inorganic dyes (GaN for the frequency of green, GaArP for the frequency of red / orange, ZnSe for the frequency of blue, GaAlP for the frequency of green) or organic, e.g. commonly used azo dyes, stable to light and temperature and soluble, such as methyl orange, methyl red, Congo red and Bismarck brown. In addition there could be DR1 (Disperse Red 1), red, and azulene, blue. Fig. 1 shows in order the formulas of the organic dyes mentioned here.

The dye or dye particle can be mixed with the material, e.g. within one of its layers or areas, before or after the spreading of the material on a support. In particular, a dye or dye particle can be mixed with each application pass in order to cover or create a layer containing a certain dye or dye particle inside.

The dyes can also be reused in the volume of material, eg. causing a layer or zone to have a dye or dye particle different from that of the adjacent layer or zone, and so on.

If organic dyes are used, it is advisable to always use only organic ones.

Inorganic dyes, on the other hand, are convenient for their very low cost and non-toxicity.

Preferably the material may comprise in general

- a solvent with a dispersed inside

- a polymer with a conjugated covalent double bond, i.e. a heterocyclic compound formed by n carbon atoms and an atom of a different type bonded in a ring structure, e.g. a thiophene or polythiophene or PATAC.

During the experiments the problem was raised of improving the characteristics of the compound, in particular lowering its electrical resistivity.

The solution to the problem was to add a dispersion of conductive particles, e.g. metallic like Ag.

The particle chain assists the polymer chains made conductive by the Laser by creating conductive bridges between the inevitable interruptions between two neighboring polymer chains, and / or creating a low resistance path in parallel to the polymer chains. The result is a reduction in the electrical resistance of the track.

It has been found that the particles, by gravity and / or specific gravity, migrate to the extremes of the layer of compound that contains them. If this layer of compound is deposited on a conductive or metal support, the conductive tracks inside the compound layer, or even the entire layer, are short-circuited.

It is necessary to solve this problem, while maintaining the conductive particles inside the compound to preserve the properties of low resistivity.

The solution is for the material to include an agent to slow down the precipitation of conductive particles within the material.

The agent blends well with the particles and supports them like a "parachute", slowing down their precipitation.

A type of agent can be silicone, which also serves to isolate conductive particles from each other before eg. a laser burns it when creating the tracks. This property is very useful when PATAC is used as a polymer.

The material / compound preferably contains in dispersion within a generic solvent all the elements described herein, preferably an aromatic solvent. In particular, it is preferred to use a benzene, and preferably a dichlorobenzene (because it dissolves thiophene and PATAC), a dichloromethane or a diluent such as nitro.

So the mixture can be spread or sprayed on any surface. It can include metal oxides, useful because they make electrons available in the matrix / compound.

In general, the polymeric matrix can comprise - as mentioned - PATAC or Thiophene.

PATAC belongs to the family of polyacetylenes, and represents a generic family of photopolymers that only require exposure to the laser to become electrical conductors due to the rupture of the lateral thioalkyl chains. After exposure to the laser, the affected areas lose part of the thioalkyl side chains and therefore a black-blue, insoluble and conductive polymer is obtained. PATAC is also a covalent conjugated double bond polymer, i.e. a heterocyclic compound consisting of n carbon atoms and a different type (or radical) atom bonded in a ring structure.

For thiophene, on the other hand, with a laser the compound is hit to excite or de-excite the thiophene molecules, sending the right energy. When they are excited their electronic state changes and they become conductors. A subsequent radiation pours energy onto the excited molecule and brings it back to its original electronic configuration state, that is, an insulator.

In particular, the laser radiation breaks the bond of the sulfur-containing radical in the thiophene, leaving the polymer chains in mutual electronic and conductive contact through the free orbital. A subsequent radiation reconstitutes the bond with the free radical and / or disconnects the thiophene chains again, and the compound returns to that insulating point.

Another type of agent as defined above can be obtained by varying the molecular density of said polymer, in particular a thiophene or polythiophene, polymer taken as an example here. That is to say that thiophene is polymerized to form longer chains, and able to slow down the conductive particles. The increased molecular mass of the polymer (a function of the polymerization time and the amount of diluent during synthesis) creates a mesh that slows down the precipitation of conductive particles.

A thiophenic chain reaches about 30 nm in maximum length, but the meshing of the chains thickens, bringing them closer, so that the gaps between the chains are smaller.

Eg. P3HT prepared as follows can be used:

- 10 gr. of 3-hexylthiophene (the monomer),

- 300 ml of chloroform (diluent),

- 20 g of FeCl3 (anhydrous ferric trichloride).

The mixture is left for 1 hour at room temperature under stirring. Then everything is filtered out. What is in the filter is the polymer (Thiophene) and it must be washed (always keeping it on the filter) with methanol. Then everything is dried in an oven at 60-70 ° C to evaporate the methanol.

At that point the polymer is ready to be dissolved in the solvent of the above compound. It has been found experimentally that e.g. passing from 300 to 250 ml of chloroform makes the product more dense, and therefore able to retain better e.g. the Ag and prevent it from settling.

The final density of the polymer in the compound which gives the described effect on the conductive particles is a function of many variables, e.g. the type of particles, the quantity and type of solvent, etc.

The thiophene or polythiophene usually produced has gaps in the molecular lattice of 500-600 nm, through which the particles (commercially available) pass.

The preparation described here has the purpose of reducing the size of these gaps (e.g. the diameter or the maximum size and / or the maximum distance between the branches of the polymer) to a maximum of 400 nm, value to which the described suspension effect of particles manifests itself.

Better and better results are obtained if these gaps or distances have dimensions less than 100 nm, preferably equal to or less than 40-50 nm. In fact, the particles can have dimensions statistically distributed in a range of values, so the percentage of smaller particles could cross the polymer chains. The smaller the size of the gaps or the distance between branches, the smaller the percentage of particles that pass the polymer lattice.

Another agent may be a resin, e.g. an organomineral resin. An example of a resin is PET plus calcium.

Preferably, the PATAC in the compound is used only as an amalgam for the components, and not to create conductive polymer chains, as does thiophene or P3HT. The PATAC is burned when the laser passes.

The compound can be applied in liquid or gelled form directly to a support or applied via a separate rigid or flexible support film or layer.

The conductivity of the compound is improved - as mentioned - by the presence of aggregates or conductive particles, such as Ag, Ni, St, Au or Pt. Silver, or one of Ni, St, Au or Pt, gave excellent results of conductivity. The silver particles, initially isolated from the polymer, stick to each other when the PATAC or thiophene or carbon polymer in the compound is hit by the Laser, and a conductive chain of contacting particles is created in the compound. Compounds such as Carbon Black and / or carbon black components and / or carbon nanotubes can be added for the same purpose.

The solvent may contain metal oxides, and / or a further component such as graphite or graphene, excellent dopants, especially due to their high electrical conductivity.

Ferric chloride or aluminum chloride, with or without coloring pigments, can be added to the metal oxides.

The metal oxides may for example consist of iron oxides in the Fe2O3 formulation, or Fe3O4 or even better, due to their better magnetization / saturation curve, of chromium oxides or dioxides, in the CrO2 formulation.

This is associated with a method for making a material within which to create an electrically conductive track or area through the variation in conductivity induced by an incident laser beam, as defined in claim 4.

A dye or dye particle is dispersed inside the material to make its absorption selective at a determined frequency of laser radiation, obtaining the advantages described above.

The preparation of the material can have different variants, according to whether it is divided into different layers or zones, and with dyes or coloring particles all different or used even more than once, see. claims 5, 6 and 7. Preferably, superimposed layers are created, although it is also possible to have areas of material which are variously positioned relatively in space and with different volume shapes.

Once the material has been prepared, it is struck in a layer or an area with a laser beam having a wavelength corresponding to the absorption frequency of the dyes or coloring particle of the area or layer itself. In this way it is possible to create an electrically conductive track or area inside a material by exploiting the selective absorption of its various parts.

A material formed by two or more layers containing different dyes or coloring particles also obtains the advantage of simplifying the method of tracing tracks that cross the layers or generally cross the largest dimension of a layer. Instead of resorting to known lasers with collimated beams or with fine power adjustment, it is sufficient to vary the frequency emitted by the laser (and possibly its power) to bring it from the absorption frequency relative to the current layer to that of the adjacent layer. In a natural way, a track is obtained that starts from the current layer and reaches the adjacent layer. By varying the frequency n times for n layers, a track is created that crosses them all. Note that non-adjacent layers can have equal laser tracking frequencies, i.e. reusable.

The advantages of the invention will be even clearer from the following description of a preferred embodiment, referring to the attached drawing in which

Fig. 1 shows the formulas of substances that can be used as dyes,

Fig. 2 shows a vertical section of the material.

In fig. 2, 10 indicates a volume of material suitable for making an electrically conductive track or area P.

The volume is formed by two superimposed layers 12, 14, and is obtained e.g. by first spreading the lower layer 14 on a support 16 (for example a wall, a sheet, a bodywork or a hull), and then adding the upper layer 12. The layers 12, 14 can be realized for example. for spreading or spraying.

The layers 12, 14 each contain dye particles or a dye, different or the same. If each layer 12, 14 is different then it is sensitive to a different laser frequency.

As shown in fig. 2. a Laser RI of a certain frequency hitting the volume 10 will be absorbed by and will have an effect only on the molecules of the layer 12, while another Laser R2, of a frequency other than RI, will be absorbed by and will have an effect only on the molecules of the layer 14. It is sufficient that the laser R1 (R2) has a color corresponding to the dye in the layer 12 (14).

Fig. 1 shows just one example of layering. Other variations include different numbers, shapes or sequences of the layers used.

In general, it is possible to spread or form a layer already containing dye or dye particles, or insert the dye or dye particle before spreading it or after it is formed or spread.

A different dye can be used for each layer than any other layer, or, to limit the number of dyes or coloring particles used, it may be sufficient that there are no adjacent layers or areas comprising dye or coloring particles of the same "color" or type,

Claims (10)

“IMPROVED MATERIAL IN WHICH TO MAKE CIRCUITS CONDUCTORS " Claims 1. Material (10) suitable for making a track (P) or electrically conductive area inside it by means of laser tracing, characterized by the fact that it comprises a dye or dye particle to absorb a certain laser radiation frequency (RI, R2). 2. A material according to claim 1, comprising two (12, 14) or more layers or zones each containing a different dye or dye particle. 3. A material according to claim 1, comprising two or more layers or zones each containing a dye or dye particle different from that present in the adjacent layers or zones. 4. Method for making a material (10) within which to create an electrically conductive track (P) or area through the variation in conductivity induced by an incident laser beam (RI, R2), characterized by the fact of (i) disperse a dye or dye particle inside the material to make its absorption selective at a determined frequency of laser radiation. The method according to claim 4, wherein in step (i) a different dye or dye particle is dispersed in distinct zones of the material to make each zone absorb a different frequency of laser radiation. Method according to claim 4 or 5, wherein overlapping layers of material are created by inserting or mixing each layer with a different dye or dye particle. Method according to claim 4 or 5 or 6, wherein superimposed layers of material are created by inserting or mixing in each layer a dye or dye particle different from the one in the adjacent layer. 8. Material or method according to one of the preceding claims, wherein the dye or dye particle is selected from GaN, GaArP, ZnSe, GaAlP, or the dye or dye particle is selected from methyl orange, methyl red, Congo red, Bismarck brown, Disperse Red 1, or azulene. 9. A material or method according to one of the preceding claims, wherein the material comprises: a solvent with dispersed inside a a polymer with a conjugated covalent double bond, i.e. a heterocyclic compound consisting of n carbon atoms and an atom of different types bonded in a ring structure, 10. Method of tracing tracks that cross layers or are transversal to the largest dimension of a layer in a material as per claims 2 or 3, in which the frequency emitted by the laser is varied to bring it from the absorption frequency of the current layer to that of the adjacent layer.