FR2818271A1 - METHOD FOR MANUFACTURING MULTI-LAYER PRODUCT, APPLICATION OF METHOD AND USE OF ASSOCIATED ADHESION PROMOTER - Google Patents

Abstract

The invention concerns a method for making a multilayer product comprising an inorganic substrate in particular of glass, said substrate being successively treated as follows: sensitizing with a tin coating, then deposition of an adhesion promoter selected from the family of mercaptosilanes having a double bond; then coating with an inorganic product such as a metal coating. The invention is characterised in that the promoter enhances adhesion between the inorganic substrate and can be selected from the family of mercaptosilanes having a double bond.

Description

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PROCESS FOR THE MANUFACTURE OF A MULTILAYER PRODUCT,
APPLICATION OF THE METHOD AND USE OF ASSOCIATED ADHESION PROMOTER
The present invention relates generally to multilayer elements formed of at least one inorganic substrate, in particular glass, coated with an inorganic product, in particular a metal layer.

 More particularly, the invention relates to the manufacture of a mirror formed of a glass substrate coated with a metal layer, for example silver.

 Traditionally, silver mirrors are produced as follows: the glass substrate is first polished and then its surface is treated with an aqueous solution of SnCl2. This treatment is commonly called sensitization treatment. After rinsing, the glass surface is usually activated by means of an ammoniacal silver nitrate treatment. The silver solution is then applied to form an opaque silver coating. The silver coating is then generally covered with a copper protective layer and then one or more paint layers to produce the finished mirror.

 The silver coating does not always adhere sufficiently to the glass substrate. In the case of some prior products, it has been observed that the silver coating spontaneously peels off the glass substrate. This is the case, for example, when the silver layer is formed from conventionally manufactured silver microbeads incorporated in a plastic matrix.

 To remedy this problem, there is known for example French patent FR 2,719,839 which describes a method for obtaining a good adhesion of a silver coating on the surface of a vitreous substrate.

 According to this prior art, the activation step is carried out by contacting the vitreous substrate not with ammoniacal silver nitrate but with a particular activation solution such as an aqueous solution of palladium chloride. In addition, this document teaches that the sensitization step must precede the activation step.

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 The activation step here aims to obtain on the surface of the glass, nodules of palladium chloride strongly bonded to the glass and which serve as a kind of attachment point for the layer of silver that is deposited. then.

 The present invention is directed to a method of manufacturing a multilayer product comprising an inorganic substrate, in particular of silico-soda-lime glass (glass obtained by the float process) coated with an inorganic product such as a metal layer.

 In accordance with the invention, the method comprises using an adhesion promoter to effect adhesion between an inorganic substrate and an inorganic product, said promoter being selected from the family of mercaptosilans having a covalent double bond.

 In addition, a specific compound has been used for adhesion purposes, quite unexpectedly. Indeed, in a known manner, this compound is used to adhere an organic product to an inorganic product.

 In a different way, the present invention aims to use an adhesion promoter to achieve adhesion between an inorganic substrate and an inorganic product.

 Advantageously, the inorganic substrate is a glass substrate and the inorganic product is a metal, in particular a metal layer.

 More specifically, said metal layer may be a silver layer.

According to the invention, the mercaptosilane is chosen from mercaptosilanes of general formula: (RO) 3 Si (CH 2) n SH with R = CH 3 or R = C 2 H 5 and O n
Preferably, R = CH3 and 0 n 3.

 In a particular way, a treatment of the surface of the glass substrate is carried out as well as sensitization before using the mercaptosilane.

 More specifically, the deposition of mercaptosilane is carried out by spraying a solution or an aqueous emulsion containing it on the glass substrate.

 In addition, the treatment of the glass surface consists of washing and brightening (or polishing).

 In addition, sensitization involves forming a tin-based layer.

 Thus, the present invention proposes, as part of a process for manufacturing a multilayer product, an improvement in the interface between two of the

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 layers and more particularly between a metal-based layer and a layer and / or a glass substrate.

 The treatment according to the invention is preferably applied to glass substrates to which a silver coating is applied to form a mirror.

 The silver coating, formed during a so-called silvering step, commonly has a thickness between 70 nm and 100 nm.

 The usual step of activation of the glass, is in fact a treatment of the glass with a given activation solution and adapted and often presents difficulties of implementation.

 According to the invention, this step is replaced by a treatment of said surface with a particular silane, more specifically with a mercaptosilane which is easy to use as will be explained below.

 Mercaptosilans are known for their ability to adhere an inorganic element such as a metal to an organic element.

 Surprisingly and unexpectedly, the present invention aims to use a mercaptosilane not to adhere an organic element to an inorganic element, but to adhere an inorganic to an inorganic and this very effectively.

 Thus, the improvement of the adhesion, according to the invention, of a coating of silver on a glass substrate could be observed in different ways: - for example, sample mirrors were subjected to an attack by hydrochloric acid vapors; the mirrors are placed on the lid of a closed chamber containing a bath of 37% hydrochloric acid. The silver side of the mirrors is placed towards the bath so that the hydrochloric acid vapors directly attack the silver side of the mirrors.

 Five different samples are tested; they were all silver in the same bath - the first one (D is a mirror with a layer of silver that has not been treated) - the second is a mirror in which the glass has been sensitized - the third The mirror CID is sensitized then activated with zero silver, that is to say with a solution of ammonium nitrate of silver, the fourth (D sample is a mirror having further undergone sensitization and then activation with palladium chloride;

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- finally the fifth &commat; is performed in accordance with one embodiment of the invention. This test made the following comparative table:

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<tb> Sample
<tb>#<SEP>#<SEP>#<SEP>#<SEP>#
<tb> Time
<tb> 10 <SEP> of
<tb> good <SEP> good
<tb> detachment
<tb> 15 <SEP> mn <SEP> Separation <SEP> Separation <SEP> 1/2 <SEP> Start <SEP> of <SEP> Start <SEP> from
<tb> total <SEP> detachment <SEP> detachment <SEP> detachment
<tb> 20 <SEP> mn <SEP> Separation <SEP> Separation <SEP> 3/4 <SEP><SEP>
<tb> total <SEP> total <SEP> detachment <SEP> detachment <SEP> Detachment
<tb> 25 <SEP> mn <SEP> Separation <SEP> Separation <SEP> Separation <SEP><SEP> Separation
<tb> total <SEP> total <SEP> detachment <SEP>%
<Tb>

This table highlights the improvement made by the invention with respect to cases (D OE) and e, three cases known and widely used so far.

 The results according to the invention are comparable to those of the case (D.

 Another type of test was performed, said BSN, short for Salt Neutral Brog, with the same samples. This test gives an indication of the aging resistance of a mirror comprising a metal film. This test involves subjecting the mirror to the action of a salt mist formed by spraying with an aqueous solution containing 50 g / l of sodium chloride.

 In this case, the samples were thus exposed 18 hours in a closed enclosure.

 Finally, a so-called ultrasonic tank disintegration test in a HCl bath was carried out with the samples (D &commat; and CID described above, the test consists in preferably immersing the samples simultaneously in a tank containing a bath hydrochloric acid, and to emit ultrasound in the bath.

The time taken to take off the money completely on each of the samples is recorded.

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Samples <SEP> Time
<tb> CD <SEP> 1 <SEP> mn <SEP> 50 <SEP> s
<tb> Ci) <SEP> 2 <SEP> mn <SEP> 20 <SEP> s
<tb>#<SEP> 2 <SEP> mn <SEP> 30 <SEP> s
<tb> z <SEP> 8 <SEP> mn
<tb> zip <SEP> 7 <SEP> mn <SEP> 40 <SEP> s
<Tb>

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Vis à vis des cas (D &commat; et &commat; on constate qu'il faut environ trois fois plus de temps pour décoller toute la couche d'argent lorsque celle-ci est déposée conformément à l'invention.

With respect to cases (D &commat; and &commat; it is found that it takes about three times longer to take off the entire silver layer when it is deposited in accordance with the invention.

 The separation times are comparable for cases z and &commat;.

 These results therefore show the improvement provided by the invention in particular with respect to cases (D &commat; and &commat;

 In fact, the differences observed are apparently due to the fact that the bonds created according to the invention would be by nature different from those previously known: the bonds according to the invention would be covalent bonds (therefore strong) and numerous with both the inorganic substrate and the inorganic coating product, whereas according to the prior art the bonds are rather of metallic type.

 Furthermore, the present invention allows real cost reductions since the mercaptosilans cost a few francs per kilo while the palladium chloride currently costs about 200 francs per kilo or three times the price of gold.

 In addition to this undeniable economic advantage, a technical advantage is related to the invention; more precisely, the use of mercaptosilane is easier than that of palladium chloride. In fact, palladium chloride precipitates as soon as it is diluted, so that when it is then necessary to spray it, there are obstructions of nozzles carrying out the spraying; this leads to a lower quality spray and the formation of a more or less homogeneous layer.

 No problem of this nature is possible with the mercaptosilane according to the invention.

 Without departing from the scope of the invention, the metal layer may be based on copper or gold.

 The concentration of the mercaptosilane is of the order of 2% in a solution which is preferably aqueous but which could be alcoholic.

Claims (12)

 1. A method of manufacturing a multilayer product comprising an inorganic substrate including glass coated with an inorganic product such as a metal layer, characterized in that it consists in using a adhesion promoter to achieve adhesion between an inorganic substrate and an inorganic product, said promoter being selected from the family of mercaptosilans having a covalent double bond.  2. Method according to claim 1, characterized in that the inorganic substrate is a glass substrate and in that the inorganic product is a metal, in particular a metal layer.  3. Method according to claim 2, characterized in that said metal layer is a silver layer.  4. Method according to any one of the preceding claims, characterized in that said mercaptosilane is chosen from mercaptosilans of general formula (RO) 3Si (CH2) nSH with R = CH3 or R = C2H5 and 0n <10 5. Method according to claim 4, characterized in that R = CH3 and 0 <n3.  6. Method according to any one of the preceding claims, characterized in that a preliminary treatment of the surface of the glass substrate and sensitization before using the mercaptosilane.  7. Method according to any one of the preceding claims, characterized in that the deposition of mercaptosilane is carried out by spraying a solution or an aqueous emulsion containing it on the glass substrate.  8. Method according to any one of claims 6 or 7, characterized in that said treatment of the surface of the glass consists of washing and brightening.  9. Method according to any one of claims 6 to 8, characterized in that the sensitization consists in forming a tin layer.  10. Method according to any one of the preceding claims, characterized in that said metal layer has a thickness of between 70 and 100 nm. <Desc / Clms Page number 7>  11. Application of the method according to one of the preceding claims to the manufacture of mirrors.  12. Use of an adhesion promoter to effect adhesion between an inorganic substrate and an inorganic product.