Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/54—Contact plating, i.e. electroless electrochemical plating

Definitions

• the present invention relates to a new method of non-electrolytic deposition of compounds, in particular electrochromic compounds, on a non-conductive solid substrate.
• the electrochromic devices typically have a structure comprising at least five layers, namely two transparent outer layers, for example two organic or inorganic glass plates, two electroconductive layers consisting for example of a doped indium oxide film. tin (indium-tin oxide, ITO) deposited on the inner face of each of the outer layers, and an electrolyte disposed between the two electroconductive layers.
• ITO indium-tin oxide
• the electrochromic compound may either be introduced into the electrolyte or be deposited on one or the other or both electroconductive layers.
• the deposition of a thin layer of at least one electrochromic compound on a substrate covered with an electroconductive layer is for example by electroplating, that is to say by connecting the electroconductive layer to an electrode and then immersing the electroconductive layer. object to be coated in a bath containing a precursor of the electrochromic compound to be deposited.
• the application of a potential difference between the electrode connected to the conductive layer and a counter electrode in contact with the bath containing the precursor of the electrochromic compound causes a redox reaction (reduction or oxidation) of the precursor of the electrochromic compound. at the surface of the conductive layer and the deposition of the electrochromic compound formed at said surface.
• the equipment for the implementation of such an electroplating process is relatively complex and requires an adaptation of the geometry of the various components of the electrodeposition device to the size of the part to be coated. A problem arises in particular for large parts on which it is difficult to obtain homogeneous deposits.
• the aim of the present invention was to propose a process for depositing electrochromic compounds on supports coated with electroconductive layers (hereinafter often called conductive layers) which would make it possible at the same time to overcome the problems of adaptation of the dimensions of the electrodeposition device to the size of the object to be coated and facilitate obtaining deposits of regular thickness over large areas.
• the process developed by the Applicant makes it possible to solve, with simple and inexpensive means, one and the other of these problems.
• the operating principle of the process of the present invention essentially consists in replacing the two electrodes of the electrodeposition device with a sufficient quantity of a redox agent deposited on a limited area of the conductive layer.
• the conductive layer in contact with the redox agent, is then brought into contact with a solution of a suitable precursor of an electrochromic compound to be deposited, an indirect oxidation-reduction reaction takes place, via the conductive layer, between the redox agent deposited thereon and the precursor in the solution.
• the precursor in solution, coming into contact with the surface of the conductive layer is reduced or oxidized and forms an insoluble compound which deposits on the surface of the conductive layer.
• the electron exchange is done indirectly via the electroconductive layer.
• the subject of the present invention is therefore a process for the non-electrolytic deposition of a compound, comprising the following successive steps: (a) depositing an electroconductive layer on a solid non-conductive substrate,
• step (c) it was necessary for each of the three agents involved in the oxidation-reduction reaction, namely, the redox agent, the conductive layer and the precursor solution of the compound to be deposited. had to be in contact with the other two. This triple contact ensures the electroneutrality of the precursor solution.
• the desired reaction did not occur when simply dipping a redox agent wire into the precursor solution in which a substrate with an electroconductive layer was immersed.
• the compound to be deposited is preferably an electrochromic compound. Therefore, the precursor in solution is preferably a compound which, after reduction or oxidation, forms an electrochromic compound insoluble in said solution.
• electrochromic compounds those in which one of the two color states is a substantially colorless state are particularly preferred.
• preferred electrochromic compounds are hexacyanometallates such as hexacyanoferrates of iron, vanadium, ruthenium, cadmium, chromium, palladium, platinum or platinum, arylviologenes and arylalkylviologenes, such as the benzyl viologen, and (C 7 _IO) -violo seeminglys such as heptylviolo faux.
• the (alkyl CI_ 6) -violo indeed despite an interesting electrochromic behavior, are water-soluble compounds, and therefore not suitable for the process of the present invention when the solution containing the precursor of compound to be deposited is an aqueous solution, which is usually the case.
• the electrochromic compound is iron hexacyanoferrate (Prussian blue) of formula
• M + Fe ⁇ Fe i ⁇ (CN) 6 where M + is a cation such as K + or 1/3 Fe 3+ , which is yellowish and water-soluble in the fully oxidized state (Fe 111 Cl 3 and K 3 Fe i ⁇ (CN) 6 ) and which forms a blue color layer, insoluble in water when in the mixed valence state (M + Fe ⁇ Fe i ⁇ (CN) 6).
• M + Fe ⁇ Fe i ⁇ (CN) 6
• M + Fe ⁇ Fe i ⁇ (CN) 6 This latter state is obtained by reducing the precursors present in the solution.
• the layer formed can itself undergo a reduction in M ' + M + Fe ⁇ Fe ⁇ (CN) 6, where M' is a cation such as for example Li + or K + , and then becomes colorless. Prussian blue is thus electrochromic with a completely colorless clear state M ' + M + Fe ⁇ Fe ⁇ (CN) 6 and a blue colored state M + Fe 11 Fe 11 ⁇ CN)
• the non-conductive substrate on which the electroconductive layer is deposited is preferably a transparent or translucent substrate. It may be a mineral glass substrate or a transparent organic substrate, for example poly (ethylene terephthalate), polycarbonate, polyamide, polyimide, polysulfones, poly (methyl methacrylate), copolymers of ethylene terephthalate and of carbonate, polyolefins, in particular polynorbornenes, homopolymers and copolymers of diethylene glycol bis (allyl carbonate), (meth) acrylic homopolymers and copolymers, especially (meth) acrylic homopolymers and copolymers derived from bisphenol-A, homopolymers and thio (meth) acrylic copolymers , homopolymers and copolymers of urethane and thiourethane, homopolymers and epoxide copolymers and homopolymers and episulfide copolymers.
• the substrate may in particular be a relatively flexible material for depositing the electrochromic compound by rotary printing.
• the electroconductive layer deposited thereon is preferably also made of a transparent or translucent material.
• transparent organic or inorganic conductive materials are known in the art.
• the most known and most widely used inorganic materials are the transparent conductive oxides known under the abbreviation TCO (of English transparent conductive oxides) among which we may mention the derivatives of tin oxide, of oxide of indium and zinc oxide.
• TCO abbreviation
• FTO fluorine doped tin oxide
• ITO indium tin oxide
• ITO indium tin doped oxide
• ITO indium tin doped oxide
• ITO Indium tin doped oxide
• an interesting organic electroconductive transparent material is poly (3,4-ethylenedioxythiophene) (PEDOT).
• PEDOT poly (3,4-ethylenedioxythiophene)
• the PEDOT is therefore generally marketed as an aqueous dispersion of a mixture of poly (3,4-ethylenedioxythiophene) and poly (styrene-sulfonate) (PSS).
• the electroconductive layer is an organic layer containing PEDOT, preferably in combination with PSS.
• the transparent electroconductive layer formed on the transparent substrate preferably has a thickness of between 10 nm and 10 000 nm, in particular between 100 and 300 nm.
• a redox agent is of course different from the material forming the electroconductive layer.
• This last remark applies in particular to the case of PEDOT which is, especially in the oxidized state, a transparent conductive polymer, and which, in the reduced state, can act as a reducing agent.
• the PEDOT can therefore act either as a conductive layer or as a reducing agent, but not both at the same time.
• the redox agent, deposited in step (b) on the electroconductive layer is preferably a reducing agent for the precursor of the compound to be deposited, that is to say a compound having a redox potential lower than the oxidation-reduction potential of the precursor couple. / compound to be deposited.
• the reducing agent is a layer containing poly (3,4-ethylenedioxythiophene) (PEDOT), generally associated with PSS.
• PEDOT poly (3,4-ethylenedioxythiophene)
• the advantage of using such a polymeric reducing agent is the ease of application.
• the PEDOT / PSS aqueous dispersion can in fact be applied manually by brush or by printing, whereas the deposition of a metal layer generally requires more complex techniques such as physical vapor deposition (PVD) and especially evaporation under vacuum (Evaporative Deposition).
• the extent of the area of the surface of the electroconductive layer covered by the redox agent is relatively small compared to that of the surface of said layer. She preferably less than 10%, in particular less than 5% and most preferably less than 2% of the surface area of the electroconductive layer. When the redox agent is nickel, this area may be less than 0.5%, or even less than 0.2%.
• redox agent to be deposited depends on the thickness of the deposit that is desired.
• a metal or polymeric reducing agent operates in the present process as a "reservoir" of available electrons, via the conductive layer, for reducing the precursor in the oxidized state in solution.
• the Applicant wishes to emphasize the great economy of the process of the present invention. Indeed, the reduction or oxidation of the compound to be deposited is very localized at the conductive layer-solution interface and not in the whole solution. As a result, there is hardly any deposition formation on the walls of the container containing the solution or the formation of a precipitate in the solution. It is thus possible to prepare a solution containing a large amount of precursor of the compound to be deposited and to use this bath for a large number of samples to be treated. Almost all the precursor will undergo a redox reaction at the surface to be treated and will be deposited on this surface. This aspect is particularly important when the compound to be deposited contains noble metals which can then be used practically without losses due to possible parasitic deposits on the walls of the apparatus.
• the concentration of the precursor of the compound to be deposited in the solution is generally between 10 -3 and 10 -1 M.
• Step (c) is preferably carried out at room temperature, that is to say at a temperature of between 15 and 30 ° C.
• the conductive layer is a transparent conductive oxide (TCO) or PEDOT
• TCO transparent conductive oxide
• PEDOT organic phosphide
• its relatively large square resistance of the order of 60 ohm / square on a plastic substrate
• electrolytic system of the present invention to deposit the redox agent at the locations and in amounts for obtaining a regular deposit of the electrochromic compound.
• the redox agent is preferably deposited at the edges of the surface of the surface.
• a conductive layer particularly preferably all around the surface of the conductive layer.
• the deposition of the redox agent in step (b) is preferably, in addition, in a regular pattern extending over the entire surface of the conductive layer but covering only a portion of it.
• the deposition of the redox agent has for example the form of a regular grid, a set of equidistant lines, a set of points uniformly distributed on the surface of the conductive layer. It is not necessary for the different deposits to be in contact with each other because each zone covered with redox agent constitutes an autonomous reservoir of electron donors or acceptors.
• the deposition of such a regular pattern of redox agent can be done according to known techniques of photo lithography comprising (a) the formation of a photocrosslinkable layer, (b) the irradiation of the areas to be crosslinked, (c) the removal of unirradiated areas (uncrosslinked), (d) deposition of the redox agent in areas not covered by the crosslinked mask, and (e) removal of the crosslinked mask.
• the deposition of the redox agent can also be used for inkjet deposition, vacuum evaporation, screen printing or stamping.
• the regular pattern applied to the conductive layer is preferably as thin as possible in order to minimize aesthetic disturbances due to uncovered areas after departure of the redox agent.
• the duration of the bringing into contact of the solution containing the precursor of the compound to be deposited with the surface of the conductive layer, in step (c), depends on the thickness of the deposit that one wishes to obtain, of the nature of the compound to be deposited, the conductivity of the conductive layer, the temperature, the concentration of the solution, etc.
• the Applicant has found, particularly surprisingly, that the rate of formation of the solid deposit on the surface of the conductive layer depends on the thickness of the nickel deposit. The thicker it was, the higher the deposition rate and the shorter the contact time.
• the contacting time of the conductive film with the precursor solution is between a few tens of seconds and ten minutes, for example between 30 seconds and 8 minutes, preferably between 1 minute and 5 minutes.
• Contacting the surface of the conductive layer with the solution can be done in a known manner, for example by immersion, centrifugal deposition, spraying, roller application, doctor blade coating.
• this contacting is advantageously done by rotary printing (roll to rol ⁇ ).
• An advantage of the process of the present invention over electroplating is that it is not necessary in principle to immerse the substrate bearing the conductive layer in the solution containing the precursor agent. This advantage is very important when other fragile deposits have been made beforehand on or under the substrate (for example deposits of transfer glues).
• the electroless deposition process comprises the following successive steps:
• Example 2 relates to the use of PEDOT as reducing agent on a layer of rro. Examples
• a layer of ITO with a thickness of approximately 200 nm is deposited on a transparent substrate made of circular poly (diethylene glycol bis (allyl carbonate)) (CR-39 from PPG Industries) of a circular shape (diameter 6.7 cm). on the edges of the sample thus obtained, nickel metal is applied by evaporation under vacuum.
• circular poly diethylene glycol bis (allyl carbonate)
• the object (CR39-ITO-Ni) is then completely immersed in an aqueous solution containing 10 -2 M FeCl 3 and 10 -2 M K 3 Fe (CN) 3. After about 3 minutes, the sample is removed from the solution and a homogeneous blue deposit is formed. The nickel deposit disappeared leaving an unstained area at the edges.
• a transparent ITO conductive film with a thickness of about 200 nm is deposited on a transparent polyethylene terephthalate (PET) substrate.
• PET polyethylene terephthalate
• an aqueous PEDOT / PSS dispersion (Baytron ® PH500
• PEDOT / PSS which, unlike nickel metal deposition, persists on the sample is also colored blue.
• Example 1 The procedure of Example 1 is reproduced using, as a transparent substrate, PET instead of CR39. After about 3 minutes, the sample is removed from the solution and a homogeneous blue deposit is formed.
• Example 1 The procedure of Example 1 is repeated using, as a redox agent, a silver-based glue deposit instead of the nickel metal deposit. After about 3 minutes, the sample is removed from the solution and it is found that a uniform deposit of blue color has formed.
• EXAMPLE 5 An ITO transparent electroconductive layer having a thickness of about 200 nm is deposited on a transparent PET substrate. Around the periphery of this layer, a metal layer of aluminum is deposited by vacuum deposition. The object thus obtained is immersed for approximately three minutes in an aqueous solution containing 5.10 3 M of heptylviologen dibromide and 10 -1 M of tetrabutylammonium perchlorate, at the end of which time the sample is removed from the solution. Pink deposition of heptylviologen dimer formed on the ITO / PET layer The aluminum metal deposition dissolved.

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• 2008
  • 2008-06-27 FR FR0854341A patent/FR2933105B1/fr not_active Expired - Fee Related
• 2009
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