Method for producing a sheet This invention relates to a method for producing an eiectroconductivesheet, this sheet comprising a substrate, in particular made of paper,- and 5 an eiectroconductive layer. This invention further relates to a method for producing a sheet, of which one side comprises a zone of greater smoothness than the rest of the side, this zone comprising a smooth external layer which extends on a surface less than that of the aforementioned side and which is an eiectroconductive layer or which is 10 intended to be covered with an eiectroconductive layer. These sheets are particularly suitable, but not exclusively, to be used in applications in electronics, such as for example in printed electronics It has already been proposed, lo produce a sheet for printed electronics using a method comprising the steps consisting of preparing a 15 multi-layer structure comprising a plastic film, a printable iayer, and an antiadhesive layer inserted between the plastic film and the printable layer, of cross-laminating the multi-layer structure and t ie substrate, removing the plastic film from the printable layer, then printing this printable layer with an ink having electrical properties. 20 However, after it is produced, this sheet is riot necessarily-electrically conductive as, although it is - printed with an ink comprising eiectroconductive particles, these particles are not interconnected to each other in such aLway as to form a continuous eiectroconductive layer. Printed electronics consists of depositing an eiectroconductive layer 25 on a supple and flexible support, such as-a plastic film, for the purpose of producing electronic components such as electronic chips, of the RFID type for example. However, although plastic films (such as those made of PEN and from PET) have a low surface roughness which is particularly interesting for 30 printed electronics, these plastic films are not very stable thermally and are 2 relatively expensive (the cosl of these films being greater than or equal to approximately 4 euros/m2). The invention has in particular for purpose to provide a simple, effective-and economical solution to the problems and needs of prior art 5 and has for purpose a method for producing a sheet, in particular with a • paper base, and comprising an eiectroconductive layer, Contrary to plastic fiims, papers and sheets with a paper base are more economical and furthermore have the advantage of being able to be recycled and of being more stable thermally. Furthermore, the use of 10 sheets or papers for printed electronics allows for the realisation of very large printed surfaces, which are more difficult to obtain using plastic films. Moreover, a sheet or a paper can be printed for an application in electronics directly after it is produced, i.e. the printing machine can be arranged directly after' the machine for producing the paper, according to a A5 continuous process froli-to-roll process). In addition, il is easier to obtain a white and glossy paper than a white and glossy plastic film because the combination of Hie gloss and whiteness properties are difficult to obtain with a plastic film, which is furthermore more difficult to cover with a coating composition in an aqueous medium than a paper which has a hydrophilic 20 nature. -•The invention proposes, for this purpose a method for producing a sheet comprising at Jeast one eiectroconductive layer, this sheet comprising a substrate, in particular made of paper, of which at least one side is covered at least partially with' a layer or with several superimposed layers of 25 'which the aforementioned eiectroconductive layer, the method comprising the steps of: a/ preparing or providing a multi-layer structure comprising at least, or comprised of, a plastic film, an anti-adhesive coating, and a base layer, with - the anti-adhesive coating inserted between a side of the plastic film and the 30 base layer, b/ gluing a side of the substrate av\<^0( the side of the multi-layer structure Located on the opposite side to the plastic film, and applying the aforementioned side of the substrate against the aforementioned side of the multi-layer structure, in such a way as to cross-laminate the multi-layer 5 structure and the substrate, c/ removing the plastic film and the anti-adhesive coating from the base layer, characterised in that the base layer Is a layer of ari electroconductive material or is covered with an electroconductive layer by an additional step consisting of: 10 d1/depositing an electroconductive film on the base layer; or <£lf printing the base layer with at least one ink having electrical properties, with the base layer being a printable layer with a binder base of which the rate Is 15% greater in dry weight in relation to the total dry matter weight of this layer, then possibly subjecting the printed sheet to an annealing heat 15 treatment In such a way as to form a layer of electroconductive ink, The base layer can be an optical and/or opto-eSectronic layer forming for example a wave guide. In this application, sheet and substrate intended for the preparation of the sheet mean a thin element (of which the thickness does not exceed 20 1 mm, and for example 0.5mm), more preferably supple and/or flexible. The method according to the - Invention defines at loasi three, separate alternative embodiments according to the nature of the base layer - of the sheet, in order to prepare a sheet comprising the desired properties. The base layer can include an electroconductive material or be 25 darned out in an electroconductive material and can therefore itself define L an electroconductive layer. The base layer can for example be formed of a metal layer. Alternatively. The base layer can be intended to be covered with an electroconductjve layer, and as such be covered with an electroconductive 30 layer which is either an electroconductive film or a layer of electroconductive ink In this latter case, the base layer is a printable layer 4 which is printed with an ink having electrical properties and which is then possibly subjected to a step of annealing in such a way as to form a continuous layer of electroconductive ink on the base layer An ink having electrical properties is an ink comprising conductive elements such as nanoparticles ancVor molecules, with these elements conferring to a sheet printed with the ink (and possibly subjected to a step of annealing) an electrical conductivity. The inventors observed that this latter embodiment made it possible to produce a sheet with good 'electrical conductivity. In a particular embodiment of the invention, the method makes it possible to obtain a sheet of which the electraconductive layer has a resistance per square less than 0,3Q/sq, more preferably Jess than 0.15ft/sq, and for example to a resistance of approximately 0 G5Q/sq, i.e. a sheet which has good electrical conductivity. This parameter can be determined by a device called a "4-tip device". The method for determining this parameter shall be described in more detail in what follows. The three aforementioned embodiments of the invention have in particular in common the producing of an electroconductive sheet, le. a sheet having an electrical conductivity that is sufficient for the purposes for example of being used in electronics. In these embodiments, the electroconductive. layer can be subjected to an additional step of, laser ablation for the carrying out of an electric circuit or other on the sheet, according to particular patterns. The method according to the invention makes it possible to carry out a sheet having an electroconductive layer with a smooth base layer (or slightly rough) and glossy. The smoothness obtained is greater than that of a sheet or of a paper produced via a conventional method, and is sufficient for the sheet to be used in the field of electronics. The roughness (AFM) of the sheet obtained by the method according to the invention is for example of approximately 10 nm. In addition, when this base layer is pnntabfe, it can be observed that, after printing, the optical density of the inks remains relatively constant over time. The more the opticaE density of the inks on the sheet In creases/varies, the more the inks penetrate deeply into the sheet and the less these inks 5 remain therefore on the surface of tine sheet, which means that the printed surface of the sheet is relatively porous (or "open") in opposition to a nonporous (or "closed") surface of a sheet whereon the inks remain on the surface !n the case with printed electronics, when the base layer is intended to to be printed with an ink having electrical properties, it is important that the base layer be the least porous possible (i.e. as closed as possible) as the fraction of the inks that penetrates into th§ pores of the sheet do not , participate in the conduction. For this, within the framework of the invention, the printable base layer comprises a binder rate which is 15% greater in dry 15 weight in relation to the tota! dry matter weight of this layer. The binder rate can be 20% greater in dry weight in relation to me total dry matter weight of this layer. It is for example between 15 and 100% and more preferably between 20 and 100% in dry weight in relation to the total dry matter weight of this layer: It can be between 15 and 50% (or between 20 and 50%), more 20 preferably between 16 and 40% (or between 20 and 40%), and most preferably between 15 and 30% (or between 20 and 30%}, in diy weight in relation to 'the total dry matter weight of this layer. In the case where the base layer comprises 100% in dry weight in relation to-the total dry matter weight of this layer, this layer does not comprise any pigments. 25 Several types of application for printed electronics exist, of which six primarily stand out. - printed circuits comprising conductive tracks, resistors, capacitors and transistors; i - photovoltaic cells, 30 - screens (etectrochromic or LCD); ssjwsii^" 6 - membrane keyboards; the sheet can then include a component or be subjected to a particular treatment in order to render it fire-retardant, the sheet can for example include flame rstardants of the aluminium trihydroxide type, for example BACO FRF40® from the Alcan 5 Chemicals company (values of 30% of BACO FRF40® in the mass of the sheet can make it possible to obtain a M1 or M2 fire classification), size press products can also be added, of the phosphorus/ammonium salts type with rates of 50% in relation to starch; other products can also be used, for example with an of ammonium polyphosphate, antimony trioxide, 10 ammonium sulpbamate, etc. base, - OLEDs (organic tight-emitting diodes) are light-emitting diodes of which the emitting material is an organic material; when a current passes through this material, it becomes a source of light; - "Switch" membranes make it possible to make a momentary connection 15 via contact; conductive ink is deposited on a flexible support of the polyester or polycarbonate type, a dome is formed and constitutes the active element of a button; under the effect of a pressure, the dome is deformed and closes the circuit; this technology is used m mobile telephones, cameras, control panels, toys, etc., and 20 - RFIO (Radio Frequency IDentificaiion) labels, also called smart labels or- . chip, tag or transponder labels are pieces of equipment intended to receive a radio signal and to send a different radio signal back as a response, containing information Those skilled in the art, specialised in printed electronics, are able to 25 determine the different layers of the sheet or of the aforementioned multilayer structure, which are required to carry out electronic components of the aforementioned type, as well as the respective arrangements of these layers in the sheet obtained by the melhod according to the invention. These different layers can be deposited onto the sheet according to the 30 invention by the same techniques as those used in prior art for the depositing of similar layers onto plastic films for printed electronics 7 The information hereinbelow substantially relates to the steps a) to c) of the method according to the invention. The multi-layer structure of the sheet can be prepared prior to implementing the method of fabrication of the printable sheet. !n this case, 5 the multi-layer structure is added in order to carry out the method of • fabrication of the sheet. According to the" invention, the base layer is prepared on a plastic film called "donor11, with this base layer, at this stage, comprised \n a multilayer structure, then is transferred onto the substrate called "receiver". This 10 technique makes it possible to transfer the smoothness of the plastic film to the base layer of which the smoothness therefore does not depend on that of the substrate used. The invention therefore makes it possible to transfer the surface finish of a plastic film onto any substrate, In other words, the invention makes it possible to produce a relatively smooth sheet using any \5 substrate, such as advantageously a rough paper and/or a paper having a relatively high bulk, for example greater than or equal to 0.9 crn^/g, even 1,10 cm3/g, and without including a plastic film in the sheet produced as such. The substrate can also be a tracing paper, a traditional paper, a lightweight paper, a coated paper, a'card stock paper, a pre-coated paper, 20 'a sheet or a plastic film, a glass slide or sheet, a sheet of metal such as sheet metal, a wooden slat, a fabric, etc r, !n this application, sheet and substrate intended for the preparation of the sheet mean a thin element (of which the thickness does not exceed 5QQfim), more preferably supple and/or flexible. 25 A multi-layer structure of the invention prepared or added in the i framework of the method according to the invention comprises- in particular, or is constituted by, a lower pEastic film, an anti-adhesive intermediary coating and an upper base layer. The anti-adhesive coating covers at least one portion of the upper side of the plastic film, and the base layer covers 3f) at least one portion of t ie upper side of the anti-adhesive coating. a The plastic film is used as a support for producing the base layer. This film does not remain in the final product, i.e Ihe sheet which can therefore be recycled The upper side of the film (located on the side of the base layer) is advantageously as smooth as possible, as the surface quality 5 of the smooth side of the sheet, defined by the base [ayer, is according to the surface quality of this upper side of plastic film. In other words, the smoother the plastic film of the mult-layer structure is, the smoother The sheet obtained is. The plastic film is chosen from among a film of polyethylene 10 terephlhalate (PET), of polyethylene (PE), of polypropylene (PPj, of polylactic acid-base polymer (PLA). of any polymer with a cellulose base, , etc The film for example has a thickness of approximately 12^m. The side of the film located on the side of the base layer is more preferably smooth and can have a Bekk smoothness greater than 1Q;0O0s 15 8ekk. The thickness, the hardness and the glass transition temperature of the plastic film have little or no influence on the characteristics of the base layer. Only the smoothness, or on the contrary, the roughness of the plastic film has an influence on the smoothness or the roughness of the base 20 iayer. The smoother the plastic film is, the smoother the base layer is Those skilled in the art are however able to determine which character sties of the plastic film are able to influence the surface finish of-the base layer, and to optimise these characteristics according to the final smoothness that is sought for this base layer. 25 -The antiradhesive coating of Ihe multi-layer structure is deposited onto the plastic film by any technique, and for example by rotogravure This anti-adhesive coating has for function to limit the adherence of the base layer on the plastic film and to facilitate the separation and the removal of the plastic film from' the. base layer in step c/ of the method defined 30 hereinabove. The anti-adhesive coating does not or hardly modifies the 9 smoothness and the surface quality of the side of the plastic film, whereon this layer is deposited. The anti-adhesive coating adheres more preferably more onto the plastic film than on the base layer, in such a way that the entire amount of 5 the coating remains glued onto the plastic film, when it is removed from the • base layer. The anti-adhesive coating has a thickness less than o^ equal to 5^171 and more preferably 1^m Its thickness is more preferably greater than 0.1 or H2|jrt. The anti-adhesive coating can be composed of silicone(s), 10 siioxane(s), poiysiloxane(s) or of its derivatives, Werner compound(s), such as chromium stearo chloride, or of polyethylene waxes, of propylene, of polyurethane, of pofyamide, potytetratluoroethyiene, of an acrylic polymer, etc Advantageously, the anti-adhesive coating does not contain any PVDF. As indicated hereinabove, according to the embodiment of t ie 15 invention, the base layer can be electroconductive or not and can .be pnntable ov not. Preferably, the base layer is free of anti-blocking agents and/or of a product able to decrease the surface energy of the layer, such as a silicone or analogous material, PVDF, PP, Teflon, silica, boron nitride, etc. This type 20 " of agent or product can be necessary for a printing a layer by heat transfer, " in particular in order to prevent the substrate from adhering to tlio ribbon of the printer. The base layer according to the invention can therefore not be printable by heat transfer. The base layer can have a thickness less than or equal to 30>m, 25 more preferably less than or equal to 15um, and more preferably less than or equal to 1 Q^m its paper weight is advantageously less than or equal to 30g/m*. more preferably iess than or equal to 15g/m;', and most preferably less than or equal to lOg/m* The base layer can for example hs^e a thickness and a paper weight which are iess than or equal to the following 30 combined values: 1G^m and IQg/m3, 3^m and 10g/m2, 2um 'and 10g/mz, 'l 10 5^m and 5g/rn2, 3^m and 5g/m:', 2j.tm and 5g/m?, 5jtm and 2g/m;', 3[ijn and 2g/m2, or 2j.tm and 2g/mz. The base layer can be deposited onto the anti-adhesive coating by any technique, and for example by rotogravure. The base layer can be deposited onto the anti-adhesive coating in • the liquid or semi-Liquid state then be solidified by drying, heating, or by electronic or UV radiation. After solidification and/or drying, the base Jayer, which is in contact with the smooth side of the plastic film by the intermediary of the anti-adhesive coating, has a smooth side, located on the side of the plastic film. The base layer is therefore dried and/or solidified before it is transferred onto the substrate, in particular in order to not modify the surface finish of this layer conferred by the plastic film, tn other words, the multi-layer structure is prepared prior to the transfer of the base layer onto the substrate, and the base layer is in the solid and/or dry state during its transfer onto the substrate, i.e. in the steps hi and c/ of the method according to the invention. The surface finish of the base layer is therefore created during the preparation of the muiti-iayer structure. In the method according to the invention, the production of the base layer is therefore carried ourt independently of that of the base substrate. This makes it possible in particular to implement the method with standard industrial tools, which allows for optimal production speeds. The base layer of the sheet can have a Sekk smoothness greater than 900 or 1000s approximately, more preferably greater than 2000s, and most preferably greater than 5000s. This base layer can have a gloss greater than 70%r and more preferably greater than 80%, this gloss being for example measured at 75 according to the TAPPI® T480 om-92 method This gloss can be similar and even greater than that of a photographic paper of the resirVcoated type, comprising a plastic film 11 "me multi-layer structure can include at least one additional layer deposited onto the base layer, on the opposite side of the plastic film, the free side of this additional layer OF of the additional layer the farthest away from the-plastic film being intended, in step b/, to be glued and applied 5 against the aforementioned side of the substrate. * The additional layer or layers can be functional or non-functional. They can for example be insulating (dielectric) or form a barrier (to gases, for example to oxygen, to liquids, for example to water, to greases, etc). The sheet can include a metal film anoVor a Barrier layer with a base 10 of polyurethane (PU), of polyvinyl alcohol (PVA), of polyvinyl dene chloride (PVDC), of vinyl acetate ethylene copolymer (EVAC), of cellulose nanofibres, or of metal, this barrier layer being located between the substrate and the base layer. A layer with a PVA base is particularly suited for forming a barrier against gases and a layer with a PU base is -.15 particularly suited to form a water vapour barrier. The electroconductive layer can act as a barrier layer, this electroconductive layer forming the external layer of the sheet or on the contrary being sandwiched between two layers of the sheet The electroconductive layer can be a metal layer vacuum deposited or a metal 20 film (such as aluminium for example), which can be.added and fixed via — cross-lamination. • The or each additional layer can be a layer of a semiconductor material {P3HT - poly(3-hexylthiophene), etc.) N-dopes, P-doped or not doped, a layer of a dielectric material (PVP, etc.), a metal layer (gold, silver, 25 aluminium, etc), a layer of electroconductive polymer (PEDQT:PSS - i poly(3,4-ethylenedioxithiophene poly(styrene sulphonate), etc.). in the case where ths multi-layer structure .comprises a single additional layer, the latter can be deposited either onto the upper side of the base tayer, i.e. onto the side of the base layer, located on the opposite side, 30 of the plastic film of the multi-layer structure, or under the base layer. i ^ - , * ? ^ ^ . . 12 This additional layer can be of any nature In the case where the multi-layer structure "comprises two or several additional layers, these additional layers are superimposed over each other and deposited onto the aforementioned upper side of the base layer. The technique or techniques 5 used to deposit the additional layer or layers onto the base layer can be of the aforementioned types, or of any other type. The multi-layer structure can therefore include in addition to the three aforementioned elements (a plastic film, an anti-adhesive coating, and a base layer), one or several additional layers on the base layer. The mufti- 10 layer structure can furthermore include a layer or a film of adhesive covering the layer the farthest away from the plastic film (i e the base layer or Hie or an additional layer), The step b/ of the method according to the invention consists of gluing the side of substrate intended to receive the base layer, or the side 15 of the multi-layer structure, located on,the opposite side to the plastic fiim, and in applying these sides against one another, in such a way as to affix them, The substrate can be chosen from among a paper, a tracing paper, a card slock paper, a coated or pre-coated paper, a sheet or a plastic film, a 20 glass slide or sheet, a sheet of metal such as sheet metal, a thin wooden slat, a fabric, etc. The paper can have a relatively substantial bulk greater. than or equal to 0.9cm3/g, even 1,1cm3/g, more preferably greater than or - equal to 1.2cm3/g, most preferably greater than or equal to 13cm3/g, more L particularly greater than or equal to 1 4cm3/g, and further more greater than -25 Or equal to 1.5cma/g i - The method according to the invention can make it possible to carry out a sheet having both a substantial bulk and smoothness, which was not possible with prior art. Indeed, it was not possible in prior art to carry out a sheet with a substantial bulk and a high surface quality A substrate having 30 a substantial bulk can be formed from an inexpensive material In the case 13 of a paper, the wood pulp used can include cellulosic fibres, a binder, and a low proportion of filters and/or adjuvants, such as starch, In a particular embodiment of the invention, the method according to the invention results in a slight decrease, by 2 to 5% approximately, in the 5 bulk of the substrate paper During the step b/ of the method, the side to be coated of the substrate or The free side of the base layer or of an additional layer of the multi-layer structure, is glued by means of a suitable adhesive Alternatively, the two aforementioned sides of the substrate and of 10 the multi-layer structure are glued simultaneously, or one after the other Advantageously, only the free side of the base layer or of an additional layer of the multi-layer structure js glued Adhesion consists of depositing a layer of adhesive on the aforementioned side or sides, via any technique, such as for example by !5 rotogravure. The adhesive can be of the thermal type, non thermal, by UV cross-linking or by chemical reaction. The adhesive can be deposited onto the or onto each aforementioned side in liquid or non-liquid form (in the case for example of a thermo-adhesivo film). This adhesive is for example' chosen ' from among the following polymers: acrylic, polyurethane, 20 polymethylmethacrylate, styrene butadiene, vinyl acetate, poly amide, nitrocellulose or any other cellulose, polyvinyl alcohol or starch The or each layer of adhesive deposited can have a thickness less than or equaf to 1G|tm, and more preferably less than or'equal to 3^rn. The adhesive is advantageocisly a single-component or , two-component polyurethane 25 adhesive, with or without solvent. " ' \n a particular embodiment of the invention, the adhesive is deposited on the aforementioned side, of the multi-layer structure during the preparation of this structure. This adhesive then is integrally a part of the multi-layer structure. The adhesive can be formed by a heat activatable 30 adhesive layer, this layer being activated by heating during the application of The multi-layer structure onto the substrate (receiver). 14 The nature of the adhesive and the adhesive process (on the film and/or on the substrate/paper) can have a substantial influence onthefinat surface finish of the sheet. It is for exampie important that the depositing of the adhesive be uniform and to prevent the formation of cavities between 5 the substrate and the base layer. With regards to the uniformity of the depositing of the adhesive, the depositing of the adhesive is more preferably homogeneous in order to prevent excess and/or lack of adhesive in locations, which wouid result in a final sheet having surface roughnesses. Advantageously, the adhesive 10 spreads perfectly over the support (film or substrate) having a suitable surface tension and rheology. The coating method of the adhesive can also have an importance, . Coating methods that generate the least amount of heterogeneity in the deposit, such as rotogravure (reverse roil or kiss coating) are preferred The 15 depositing is more preferably chosen in order to fill to the maximum the pores or surface irregularities of the substrate. By way of example, when a paper has an average surface roughness (for example Sa) of approximately 20pm, a depositing of adhesive having a thickness of.at least 10pm is preferred in order to fill in the pores The depositing of adhesive is more 20 preferably carried out on the substrate when the tatter is too rough If the depositing on a paper is insufficient, cavities are then formed between the surface of the paper and the base layer. During printing, these cavities will becomes weak'points for the paper which could then either sink, if a pressure is exerted, or be pulled off, if a traction is exerted. 25 Advantageously, the' thickness of adhesive deposited onto the i substrate and/or the base layer is equal to at least half of the average surface roughness (for example Ra or Sa) of the substrate, in an embodiment of the invention, the adhesive is deposited on at ieast one side , of the substrate in step b/, and- the thickness of the layer of adhesive 30 deposited is at least equal to half of the average roughness of the side of the substrate, and is more preferably equal to this average roughness. 15 The adhesive can be with a water base, solvent, without solvent, two-component or single-component. The adhesive makes it possible to fix the base layer (or an additional layer) onto the substrate and, where applicable, to compensate the surface irregularities of the substrate. The adhesive in particutar fills in the hollows of the side to be coated of the substrate and thus makes it possible to flatten this side, without however modifying Ihe characteristics of the substrate, such as its bulk. The substrate of the sheet can include fillers intended to increase the thermal diffusivity of the sheet and/or to increase the wel strength of the sheet and/or to render the sheet fire-retardant, as shall be explained in more detail in what follows. The slep b/ of Ihe method then consists of applying the aforementioned side of Ihe substrate onto the aforementioned side of the multi-layer structure, in such a way as to laminate them OF cross-laminate them. The base layer is then sandwiched between on Ihe one hand the substrate and the adhesive (and where applicable one or several additional iayers), on one side, and on the other hand the plastic film and the antiadhesive coating, on the other side. In The case where Ihe adhesive used for gluing the substrate onto the multi-layer structure is of the ihermo-adhesive type, the application of the substrate onto the muiti-layer structure is carried Lout hot, at a given temperature, which is fonexample between 50 and 200"C approximately. Alternatively, the application and Ihe gluing of the substrate onto the multilayer structure can be carriedout at ambient temperature A pressure can be necessary in order to provide good adhesion of the base layer on the substrate, by the intermediary of the adhesive. The temperature and/or the pressure used during the application and Ihe gluing must not however modify the characteristics of the base layer, and in particular Ihe surface finish of its side located on the side of the plastic film. For example, the base iayer must not be softened by the 16 application of a high temperature, because this couEd result in a modification and/or a decrease in the surface quality of its side, located on the side of the plastic film. The step c/ of the method then consists of removing the plastic film from the base layer and from the substrate, in such a way that the base • iayer {and where applicable the aforementioned additional layer or layers of the mufti-layer structure) remain on the substrate The base layer, and where applicable the additional layer or layers, are therefore transferred from Ihe plastic fiim called donor, of the multi-layer structure, onto The substrate called receiver The method can further include a step of cross-linking or matunng of the adhesive before removing the film. As explained hereinabove, the entire amount of the anti-adhesive coating remains more preferably on the plastic film and is then removed fromrthe base layer, during the removal of the plastic film. The side of the base layer, which was located on the side of the plastic film in the multilayer structure, is therefore exposed. The transfer of the base layer of the multi-Layer structure onto the substrate, in the steps b! and c/ of'the method, can be carried out in the ' following manner, when the substrate and the multi-layer structure have the form of continue us -strips. The laminating or cross-laminating of the multi-layer structure and of 'the substrate can be carried out by passing these two elements"between two adjacent and parallel mechanical rollers, rotating in opposite directions. The thickness of the product obtained is in particular according to The . distance between the rollers. Once the adhesive is dry or .solidified, the - plastic film is removed from the sheet while the latter is driven by another mechanical roller. Alternatively, either the mult-layer structure or the substrate can be glued, dry the adhesive, then place these two elements in contact with each other by applying a determined temperature and pressure. 17 The method can further consist in that, before ihe step b/, the aforementioned side of the substrate is pre-coated with at least one i smoothing layer comprising one or several thermoplastic polymers (such as at least one polystyrene, a polyurethane, an acrylic, eta,) OF a mixture of 5 pigments (such as kaolins, calcium carbonates, talc, titanium dioxide, etc, and their mixtures) and of at least one binder (such as with an acrylic base, polyurethane, polymethylmethacrylate, styrene butadiene, vinyl acetate, polyamide, nitrocellulose or of any other cellulose, starch or PVA) This pre-coated side of the substrate can furthermore be calendared, 10 before the step bi, in order to increase its smoothness. With regards to the step d1/ of depositing the efectroconductive film, . this film can be formed of metal or of conductive polymer or any olher electroconductive material. It can be produced independently of ihe sheet then be added and affixed, for example by gluing, onto the base layer of the 15 sheet. Alternatively, it is formed in situ on the base.layer of the sheet The information hereinbelow relates to the step d2/, according to which the base layer is printable, A printable layer is a layer that can be printed by any printing "technique, and in particular by Offset, ink jet, laser, heliography, 20 flexography, screen printing, dry toner, liq'Liid toner, electrophotography, lithography, etc.-printing. A printable layer comprises a binder and can further include pigments. According to a characteristic of the invention, the printing of the base layer does not result in any structural modification of the latter, and in 25 particular any .change in the state-or phase of the latter (such as for .example a passing from a solid state to a liquid state and then returning to the solid state). When the base layer of the multi-layer structure is a printable layer, it can be chosen from among a printable varnish, a pa permeating, etc. 30 In this application, printable varnish means a substance with a base of acrylic polymer, polyurethane, poly methylmethacry late, styrene 1% butadiene, vinyl acetate, poiyamide, nitrocellulose or of any other cellulose, polyvinyl alcohol, starch, etc. This substance is in general deposited in the liquid form and solidified by drying/heating or by UV radiation or electronics Paper coating or coating composition means a composition 5 comprising a binder and possibly pigments The binder of One printable base layer can include a main binder and possibly a co-binder. "In this application, main binder means a binder which is the majority in the layer in relation to the other binders, in particular in relation to the cobinders). 10 The main binder is advantageously • a synthetic latex such as a styrene-butadiene copolymer (XSB) and/or a styrene-acrylate copolymer (SA) The binder can include a combination of two latexes, such as XSB and SA, in proportions between 55 and 80% for XSB and between 20 and 45% for SA (in dry weight in relation to the total dry weight of these - 15 binders), even between 60 and 70% for XSB and between 30 and 40% for SA (in dry weight in relation to the totai dry weight of these binders). The base layer can include a binder with an acrylic base, polyurethane, polymethylmethacrylate, styrene butadiene, vinyl acetate, poiyamide,' nitrocellulose or of any other cellulose, polyvinyl alcohol, starch, or a 20 • mixture of the latter. The co binder is. more preferably an adhesion promoter with an ethylene copolymer - acrylic acid (EAA) base. This co-binder can make it possible to increase the gloss of the base layer and to improve the adhesion phenomenon of certain inks on the base layer, such as liquid "25 toner inks of the HP indigo type. The pigments can be the majority in relation to the binder in a paper coating. The pigments have for example an average size or an average diameter less than or equal to 2j.Lm environ, even 1 yxn, and for example of approximately 0,5jtm, The pigments can be chosen from among- the 30 calcium carbonates, kaolins, titanium dioxide, talc, silicas, mica, and pearlescent particles, plastic pigments (polystyrene (PS), polyurethane 19 (PU), styrene-acrylic, etc. - such as the Ropaque Ultra-E pigment from the Rohrrt&Haas company), metal pigments (silver, copper, or, etc. - such as the Brookprint Sparkle Silver pigment from the Rondot S A company), and their mixtures. These are advantageously caEcium carbonates 5 The plastic materiaE used in the base layer (as a binder and/or pigments) is easily fragmented and does not pollute the wood pulp when it is recycled. On the contrary, the plastic films retain a cohesion and clog the fitters during the putting back into suspension of the wood pulp. The watersoluble binders (such as starch, polyvinyl aicohol fPVA), etc) are 10 particularly advantageous for this subject as they are dispersed in the water during recycling. The paper coafrng can further include a dispersant and/or a rheology modifier and/or a.colouring agent and/or a surfactant or spreading agent and/or a conductive additive This conductive additive can be used to 15 decrease the surface resistivity of.the sheet. The pnntable base layer can be formed of two or more underlayers superimposed on one another, with each underiayer being printable and being chosen from among the aforementioned types (printable varnish, paper coating, etc.) 20 Advantagsqusly, in the case where the paper forming the substrate of the sheet is a tracing paper.-the printable base layer has a transparency and a binder rate greater than 30% in dry weight in relation to the totaE dry matter weight of the layer,'in such a way that the sheet obtained par the method has a certain transparency. The use of a tracing paper is 25 particularly advantageous in order to authorise the passage and the .recovery of radiation energy through the sheet, and is therefore particularly suited for the carrying out of photovoltaic or solar cells. The transparency of a tracing paper depends in particular on its paper weight and is for exampte of approximately 60-70% for a tracing paper of 62g/m? and 40-50% for a 30 tracing paper of 175g/m2. 20 The ink can for example include n a nop articles or metal micro particles (silver, copper, or, etc.), nanoparticEes or microp articles of carbon, and/or at least one conductive poEymer (such as PEDOT/PSS). The metal particles can be in the form of a powder. There are 5 therefore spaces between them when they are deposited onto the base layer. The step of annealing makes it possible to coalesce or to sinter the - nanoparticEes together and as such authorise the passing of current between the Latter. The conductive layer deposited has for example a Thickness less than or equafta 1^m, which can be Jess than or equal to K) 300nm, and which is for example of approximately 3Qnm. This relatively low thickness makes it possible however to confer good conductivity to the _ sheet. Indeed, due to the substantial smoothness of the base Eayer, it is not required to deposit a thick conductive layer onto the base layer because the thin layer of ink remains continuous on the surface. It can be considered to 15 deposit a layer of goid with a thickness between 20 and 1G0nm, and for exampEe between 30 and 40nm environ The annealing can be carried out in an oven (for example, at a temperature between 150 and 200DC and for 5 to IGmirc approximately), on' a Hot plate, in a photon oven or in an infrared dryer. The photon oven (for 20 example the PulseForge® 3300 device from the NovaCentrix company) makes it possible to carry out an effective, sintering of the conductive particles of the inks, which are more preferably deposited ontq the base layer -by screen printing. The conductive particles can be particles of silver, copper, various alloys, etc This is for exampEe carried out at a temperature 25 greater than or equal to 100aC, more preferably greater than dr equal to 120°C, and most preferabiy. greater than or equal to 150DC, which is highly advantageous as this makes it possible to obtain a good cohesion of the etectroconductive materials or particEes of the inks and therefore provide a better electrical conductivity for the layer, with the'sheet having ah excellent 30 thermal stability at 15G-170°C. The plastic films (PET, PEN, etc.) from prior art cannot be subjected to such annealing temperatures because they I 21 break down in genera! starting at 120-140UC. The annealing time can be less than or equal to 5 minutes and is for example between 2 and 3 minutes The annealing can be carried out by maintaining the sheet in traction (along an axis or two perpendicular axes, for example) in such a 5 way as to limit the variations of the dimensions of the sheet during - annealing. Generally, the sheet has good thermal and dimensional stabilities during annealings or during any such treatments. The method according to the invention can further include one or several of the following steps: 10 - before the step d2/, a step of heat .pre-trealment of the sheet in order to remove at least one portion of the water that it contains; a paper can include approximately 5% in water weight; the heat pre-treatment makes it possible to remove the water from the sheet in such a way that the sheet " printed and subjected to annealing1 substantially no longer contains any 15 water, this makes it possible to limit the risks of rippling and of deformation of the sheet during annealing due to t ie evaporation of the water contained in the paper of this sheet; - removing via photolithography or via laser ablation certain predetermined' zones-of the electroconduclive layer of the sheet; 20 -.repeating at least once the step d2/, with each step d2/ which follows a ---step d2/ being separated from this step by an intermediary step of rest of the sheet, during which the sheet js intended to substaniiaiiy^recover its initial humidity rate; and - carrying out, before the step d2/, a step consisting of subjecting the base layer to a plasma treatment; this treatment makes it possible to modify the surface finish of the'base layer and to render it more hydrophobic, which makes it possible to prevent the ink from spreading out and wetting the . base layer too much {and resulting in an increased precision and resolution in the patterns printed on The layer); advantageously, the base iayer is subjected to a fluoride plasma treatment (SFC) • ^ • " ^ ^ ^ ^ i - - - - . ^ ^ 25 -^JS^sfet22 The. method can further include a step consisting of carrying out with the sheet at least one resistor, a capacitor, a transistor, an RFiD chip, an antenna, a logic circuit, a membrane switch (SWITCH), a photovoltaic celi, a battery, a means for collecting energy, a backlighting system, a means of 5 solid-state lighting or display such as an organic or inorganic light-emitting diode (OLED), a sensor, a membrane keyboard, or any combination of these components. The method can furthermore be characterised in that: (i) in the multi-layer structure prepared in step a), the base layer extends on 10 a surface less than that of the aforementioned side of the plastic film, and/or (ii) the multi-layer structure and the substrate are cross-laminated in step b) on a surface less than that of the aforementioned side of the sheet, and/or (iii) the plastic film removed in step c) has at least one dimension among Us \5 length and its width which is less than the corresponding\dimension or dimensions of the aforementioned side of the sheet, and/or (iv) the sheet obtained in step c) is cut then at least one cut piece of this sheet is glued onto the substrate of another sheet, in such a way that the sheet comprises at least one-side having at least one 20 zone of greater smoothness than the rest of t^is side, this zone comprising a smooth external layer which is formed by the base layer and which extends over the substrate of the sheet on a surface less than that of said side. The method can include, between the steps a) and b), a step of 25 cutting of themulti-layefstructure Preferably, at least one cut piece of the multi-layer structure is crosslaminated to the substrate in step b), and the plastic film and the antiadhesive coating are removed from the glued piece, in step c), the cut piece being for example in the form, of a strip "having a Length of several 30 metres. •, 23 Preferably, t i e application of the muiti-layer structure on the substrate is realised in step b) by means of a stamp press which is intended to apply a pressure in the aforementioned zone, or by means of a hot foil stamp press which makes it possible \o soften the adhesive used in step b). 5 which is of The heat-sensitive type Preferably, the plastic film of the multi-layer structure prepared in step a) has at least one dimension among rts length and its width which is less than the corresponding dimension or dimensions of the aforementioned sioe of the sheet. 10 Preferably, the sheet is carried out on line in a paper machine, for example in a Una! section of drying of this paper machine, or off Sine in a paper cutting or finishing machine The method can include, before the step c). a step of printing the side of the multi-layer structure located on the opposite side of the plastic 15 •'film with electroconductive inks, or of depositing an electroconductive coating onto this side. Preferably, during the step a), the anti-adhesive coating deposited onto the plastic film is printed with electroconductive inks or is covered with an electroconductive coating. "20 Advantageously, in the aforementioned case (iv), the sheet to be cut or the cut piece is printed with electroconductive inks or is covered with an electroconductive coating, before the gluing onto the substrate of the other sheet. The invention further relates to a method for producing an 25 electroconductive product comprising the carrying out, by means of a"sheet, more preferably, obtained by a method such as described hereinabove, of at ieast one resistor, a capacitor, a transistor, an RF1D chip, an antenna, a logic circuit, a membrane switch (SWITCH), a photovoltaic cell, a battery, a means for collecting energy, a backlighting system, a means of solid-state 30 lighting or display such as an organic or inorganic light-emitting diode (OLED), a sensor, a membrane keyboard, or any combination of these 24 components, in particular by implementing a step of printing of the base layer and/or a step of removing via photolithography or via laser ablation of certain predetermined zones of the eiectroconductive layer. The invention further relates to an electroconductive product. 5 characterised in that it comprises a sheet, more preferably, such as -i obtained by a method such as described hereinabove, said sheet being converted into a product comprising ai least one resistor, a capacitor, a transistor, an RFID chip, an antenna, a fogic circuit, a membrane switch (SWITCH), a photovoltaic cell, a battery, a means for collecting energy, a ^0 backlighting system, a means of solid-state lighting or display such as an organic or inorganic light-emitting diode (OLED), a sensor, a membrane •i keyboard, or any combination of these components, in particular by implementing a step of printing of the base layer and/or of a step of removing via photolithography or via laser ablation of certain predetermined 15 zones of the eiectroconductive layer in the aforementioned case, the treated side of each sheet is entirely coated with the multi-iayer structure of which the plastic film is intended to be removed. Substantial quantities of plastic film, of anti-adhesive coating and of adhesive can therefore be used, which increases the cost of the final" 20 product , Due to the increase in this cost, the method can be reserved for specific applications and may not "be able to be used in other applications. Moreover, the step of laminating a paper requires, due in particular to the dimensions of the multi-layer structure, a particular machine which is 25 intended to treat the paper after it is produced by a paper machine, i,e. off tone. Another aspect of the invention ha$ in particular for purpose to provide a simple, effective and economical solution to this problem. It proposes for this purpose a method for producing a sheet of which 30 at least one side comprises at least one zone of greater smoothness than the rest of the side, this zone comprising a smooth external layer which 25 extends over a substrate of the sheet on a surface less than that of said side, the method comprising the steps of: a/ preparing or providing a multi-layer structure comprising at least, or comprised of, a plastic film, an ant-adhesive coating, and a bass layer, with the anti-adhesive coating inserted between a side of the plastic film and the • base layer, b? gluing a side of the substrate and/or the side of the multi-layer structure located on the opposite side to the plastic- film, and applying the aforementioned side of the substrate against the aforementioned side of the multi-layer structure, in such a way as to cross-laminate the multi-layer structure and The substrate, c/ removing the plastic film and the ,anti-adhesive coating from the base layer, with the base layer defining said smooth external layer, characterised in that: (i) in the muiti-layer structure prepared in step a), the base layer extends on a surface less than that of the aforementioned side of the plastic film, and/or (ti) the multi-layer structure and the substrate are cross-laminated in step b) on a surface less than that of the aforementioned side of the sheet, (iii) the plastic film removed in step cj has at least one dimension among its -length and its width which is less than the corresponding dimension or dimensions of the aforementioned side of the sheet and/or (iv) the sheet obtained in step c) is cut then at least one cut piece of this sheet is glued onto the substrate of another sheet. In this application, the zone (of a side) of the" sheet means a portion - only (of The side) of the sheet The zone has for example at least one dimension among its length and its width which is less than the corresponding dimension or dimensions of the sheet. The zone can for example have the form of a strip and extend along one of the .longitudinal' edges of the sheet The zone can have a surface representing less than 26 50%, more preferably less than 20%, and most preferably less than 10%, of the surface (of the side) of the sheet. According to the invention, a portion only of the side of the substrate of the sheet is covered with the aforementioned smooth externa! layer. This is particularly advantageous as this makes it possible to use quantities of plastic film, anti-adhesive coating and/or adhesive that are less than those used in prior art and therefore make it possible to-reduce the cost of producing the sheet and to consider multiples applications that were not able to be considered in prior art for economical reasons. In a particular case of producing a paper, the extra cost linked to the application of the method to this paper is relatively low. which makes it i possible to consider the use of the paper in several different applications. The aforementioned external layer confers a relatively substantial smoothness to tine zone, which is greater than that of the rest of the sheet i.e. than the portions of the sheet that do not comprise this layer. This smoothness is induced by that of the plastic film of the multi-layer structure, and therefore does not depend on that of the base substrate used. By way of example, the or each aforementioned zone can have a Bekk smoothness greater than 900s (more preferably greater than 1000s, and'most preferably greater than ,2000s), With the rest of-the sheet having a Bekk smoothness less than 900s (more preferably less than 500s, and most preferably less .than 200s) ' . . Moreover, the base layer can have magnetic properties (in particular ferromagnetic in the case de carrying out self-inductance, coil and antenna) or other properties such as in particular a barrier property (the base layer can be associated with an aluminium film or \~iave properties close to those of an aluminium film), a property that modifies its appearance (the base layer can be coloured, reflective, etc.), an opto-electronic or optical property (the. base layef can form a wave guide), -and/or a security function (The base layer can include a micro-print, a hologram, be iridescent, etc ). 27 The sheet according to the invention furthermore has a clear advantage in terms of recycling' because the portions of the sheet that are not covered with a smooth base layer can be recycled convent!onally, The smooth portions of the sheet can be deiaminated or cut in order to be recycled independently from the rest of the sheet in order to recover any electroconductive materials that it contains.H The multi-layer structure can include more than one layer, i.e. it can include one or several other layers inserted between the anti-adhesive coating and the base 'layer. In the case of multi-layer structures, the advantage is that the-smoothness of the first layer is transmitted to the following layer. This is all the more so interesting in thai the thermal stability of the paper allows ,for a stable stack providing an optical and electrical quality of the system to be carried out over a large surface (as successive annealing temperature are high and therefore the losses of fillers are low over long distances due to the excellent conductivity) In tie case of transparent electroconductive layers (of the PEDOT:PSS type for example), the thermal annealing is the only way to have the conductivity (flash sintering cannot be used due to its transparency), yet this layer is generally one of the last to be applied to the substrate in the case of multi-layer systems. Our ultra-smooth paper therefore makes it possible to reduce the quantity of Transparent conductive polymers to be applied. In the aforementioned first case (i) of the method according to the invention, in the multi-layer structure prepared in step a), the base layer i extends on a surface less than thafof the aforementioned side of the plastic film. The base layer therefore covers only a portion of the plastic film The anti-adhesive coating which is sandwiched between the base layer and the plastic film can cover the entire amount of the plastic film or a portion only de this film. Advantageously, the base layer substantially covers the entire amount of the anti-adhesive coating which covers only a portion of the 2S plastic film. The base layer can have a shape and dimensions similar to those of the zone of greater smoothness to be formed on The sheet. In the aforementioned second case (It) of the method, the multi-layer structure and the substrate of the sheet are cross-laminated in step b) on a surface less than that of the sheet. The adhesive can be deposited onto a i portion only of the multi-layer structure and/or on a portion only of the substrate of t i e sheet. The glued portion or portions can have a shape and dimensions that are similar to those of the zone of greater smoothness to be formed on the sheet. The cases (i) and (ii) can be combined. In Ibis case, the base layer extends on a surface less than that of the plastic film in the multi-layer structure prepared in step a), and the multi-layer structure and the substrate of the sheet are cross-laminated in step b) on a surface less than that of the sheet. In the aforementioned case (lii) of the method, the plastic film removed m step c) has at least one dimension among its length and its width which is less than the corresponding dimension or dimensions of the aforementioned side of The sheet. The cases (i) and (lii) can be combined. The base layer extends on a surface less than that of the plastic film in the multi-layer structure prepared in step a),-and the plastic film removed in step.Q). is smaller than She sheet. The cases (ii) and. relation to the total dry matter weight of the base layer. 10: Method according to one ot the preceding claims, characterised in 25 that it comprises, before the step d2/, a step of heat pre-tre'atment of the sheet in order to remove at least one portion of the water that it contains. 11. Method according to one of the preceding claims, characterised in that the annealing is carried out in an oven, on a hot plate, a photon oven or in an infrared dryer ' - ^ 30 12. Method according to one of the preceding claims, characterised in that the step d2/ is repeated at least one time, each step d2/ which follows a 66 step d2/ being separated from this step by an intermediary step of rest of the sheet, dunng which the sheet is intended to-substantially recover its initial humidity rate. 13. Method according to-one of the preceding cfaims, characterised in 5 that the step 621 is preceded by a step consisting of subjecting the base layer to a plasma treatment. 14 Method according to one of the-preceding claims, characterised in that the adhesive (26) used in step b) is a single-component or twocomponent polyurethane adhesive, with or without solvent 10 15, Method according to one of the preceding claims, characterised in that the substrate comprises fillers intended to increase the thermal diffusivity of the sheet and/or to increase the wet strength of the sheet . and/or to render the sheet ft re-retard ant. 16. Method according to one of the preceding claims, characterised in 15 that: (i) in the multi-layer structure prepared in step a), the base layer extends on a surface less than that ot the aforementioned side of the plastic film, and/or fii)' the multi-layer structure and the substrate are cross-laminated in step b) 20 on a surface less than- that of the aforementioned side of the sheet, andtor (iii) the plastic film removed in step c)-has at least.one dimension among its length and its width which-is less than the corresponding dimension or dimensions of the aforementioned side of the sheet, and/or (iv) the sheet obtained in step c) is cut then at least one cut piece from this 25 sheet is glued onto the substrate of another sheet, in such a way that the sheet comprises at least one side having at least one zone of greater smoothness than the rest of this side, this zone comprising a smooth external layer which is formed by the base layer and which extends over the substrate of the sheet on a surface less than that of said 30 side. 67 17. Method according to ctaim 16, characterised in that it comprises, between the steps a) and b), a step of cutting of the multi-layer structure (12). 18. Method according to cfaim 17, characterised in that at [east one cut 5 piece (104) of the multi-layer structure (12) is cross-laminated to the substrate in step b), and the plastic film (14) and the anti-adhesive coating (16) are removed from the glued piece, in step c), with the cut piece being" for example in the form of a strip (104) having a length of severai metres. 19. Method according to one of claims 16 to 18, characterised in that the LO application of the muiti-layer structure (12) onto the'substrate (24) is carried out in step b) by means of a stamp press which is intended to apply a pressure in the aforementioned zone, or by means of a hot foil stamp press which makes it possible \o soften the adhesive used in step b), which is of the heat-sensitive type. t5 20. Method according to one of claims 16 to 19, characterised in that the plastic film (14) of the muiti-tayer structure (12) prepared in step a) has at feast one dimension among its length and its width which is less than the corresponding dimension or dimensions of the aforementioned side of the sheet. 20 21. Method according to one of claims 16 to 20, Characterised in that the sheet (10) is carried-out on line in a paper machine,-for-example in a-final drying section of this paper machine, or off line in a paper cutting, or finishing machine 22 Method according to one of claims 16 to 21, characterised in that it 25 comprises, before tfle step c), a step of printing the side of the multi-layer structure located on . the opposite side of the plastic film with eEectroconductive inks, or of depositing an electroconductiye coating on this side. 23. Method according to one of ciaims 16 to 22, characterised in that, 30 during the step a), the anti-adhesive coating deposited onto the plastic film 68 is printed with electroconductive inks or is covered with an electro conductive coating. 24. Method according to clapm 16, characterised in that, in the aforementioned case (iv), the sheet to be cut or the cut piece is printed with 5 electroconductive inks or is covered with an electroconductive coating, • before the gluing onto the substrate of the other sheet. 25. Method for producing an electroconductive product comprising the carrying out, by means of an electroconductive sheet obtained by a method according to one of the preceding claims, of at least one resistor, a 10 capacitor, a transistor, an RFID chip, a logic circuit, a membrane switch (SWITCH), a photovoltaic eel!, a battery, a means for collecting energy, a backlighting system, a means of solid-state lighting or display such as an organic or inorganic Sight-emitting diode (OLED), a membrane keyboard. and a sensor, • or any combination of these components, in particular 15 through the impiementation of a step of printing of the base layer and/or of a step for removal via photolithography or via laser ablation of certain predetermined zones of the electroconductive layer. 26. Electroconductive product, characterised in that J6 comprises an • eieciroconductive sheet such as obtained by a method according to any of 70 claims 1 to 24, said sheet being converted into a product comprising at . least-one-resistor, a capacitor, a.transistor, an RFID chip, a logic circuit, a membrane -switch (SWITCH), a photovoltaic cell, a battery, a means for collecting energy, a backlighting system, a means of solid-state lighting or display such as an organic or inorganic iight-emitting diode. (OLED), a 25 membrane keyboard, and a sensor, or any combination" of; these components, in particular through the implementation of a step of printing of . the base layer and/or of a step or removing via photo lithography or via laser ablation of certain predetermined zones of the electroconductive layer. 27 Electroconductive product according to claim 26, characterised in that . . 30 the electroconductive layer has a resistance per square fess than 0 3 p/sq. " more preferably less than 0.15 illsq, and for example to 0.05n/sqr