Forming a silver coating on a vitreous substrate

& Quot; FORMATION OF A SILVER FINISH ON A SUBSTRATE VITREOUS & quot;

DESCRIPTION The present invention relates to a process for forming a silver coating on a surface of a glass substrate, in particular refers to the glass silvering, i.e. the electroless deposition of a silver coating, by using a silvering solution.

Such a coating can be deposited according to a defined pattern to form a decorative article, but the present invention is of particular interest in the case of glass substrates bearing a continuous reflective coating. The coating may be applied to a substrate in any form, for example to an artistic object, to achieve a particular desired decorative effect, but it is demand that the invention finds its greatest use when the coating is applied to a glass substrate plan. The reflective coating may be so thin that take transparent. The glass plates that support transparent reflective coatings are useful inter alia as sunscreens or as low emissivity panels (relative to infrared radiation). Altemativamente, the coating may be fully reflective, thus forming a mirror-coating. Such a process is also employed for forming silver glass microbeads (i.e., microbeads bearing a silver coating), which may, for example -2- be incorporated in a plastic material matrix to form a reflective marking paint roads or a conductive plastic material.

In a conventional manner, silver mirrors are produced as follows. The glass is polished in the first place and then sensitized, typically employing an aqueous solution of SnCl2. After washing, the glass surface is usually activated by a treatment with ammoniacal silver nitrate. The silvering solution is then applied to form an opaque coating of silver. This silver coating is then coated with a protective layer of copper and then with one or more layers of paint in order to produce a finished mirror. The silver coating does not always adhere sufficiently to the substrate. In the case of certain products in the past, it was observed that the silver coating spontaneously out of the glass substrate. This is for example the case in which silvered microbeads made by a normal process are incorporated into a plastic matrix. The object of the present invention to improve the adhesion of such a silver coating to glass and thereby improve the durability of the silver coating.

According to a first aspect of the invention, there is provided a process for forming a silver coating on a surface of a glass substrate which comprises an activation step, whereby said surface is contacted with a activation solution a sensitization step according to which the surface is contacted with a sensitizing solution and a subsequent step of silvering whereby said surface is contacted with a silvering solution, which is composed of silver source to form the silver coating, and is characterized in that said activating solution comprises ions of at least one of bismuth (III), chromium (II), gold (III), indium (III), nickel (II ), palladium (II), platinum (II), rhodium (III), ruthenium (III), titanium (III), vanadium (III) and zinc (II). The feature of the invention is to "activate" the substrate by treating it with a specific activation solution before silvering.

It was observed that treating glass with an activation solution according to the present invention improves the adhesion of the silver coating. The sensitization step helps to improve the adhesion of the silver coating and therefore its durability. Preferably the sensitizing step is performed before the silvering step. This sensitization step is typically carried out with a sensitizing solution comprising tin (II) chloride.

Preferably, said sensitization step is performed before the activation step. It was observed that the order of steps embodiment is important for achieving good durability. This observation is very surprising because the activation treatment does not really produce a distinct continuous layer containing bismuth (III), chromium (II), gold (ΠΙ), indium -4- -4-

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\ (III), nickel (II), palladium (II), platinum (II), rhodium (III), ruthenium (III), titanium (III), vanadium (III) and zinc (II), but "islets" on the same glass surface. An analysis of the glass surface treated with a sensitizing solution containing stannous chloride (Π), and then treated with a palladium-containing activating solution (II) shows the presence of a certain proportion of palladium atoms from the backbone atoms of tin on the glass surface. Typically, palladium is 0.4 atoms per atom of tin, and 0.3 tin atoms per Si atom on the glass surface. The activation treatment according to the present invention can be carried out on various types of vitreous substrates, for example on glass microbeads. It was observed that the treatment according to the invention improves the adhesion of the silver coating subsequently deposited on the glass microbeads. When these silver microbeads are incorporated into a plastic, it is discovered that the silver coating has less tendency to pelt of pearls than the activation treatment according to the invention is omitted. The invention may also be implemented on flat glass substrates, and it is believed that the invention will be particularly useful for this type of substrate. Consequently, treatment is preferably performed on a glass substrate such as a glass plate. The silver layer can be deposited as a silver coating is so thin so it becomes transparent. The flat glass substrates supporting such transparent coatings are employed to form glass panels which reduce the emission of infrared radiation and / or which protect from solar radiation. Thus, according to

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one embodiment of the invention, the thickness of the layer of silver formed in said silvering step is between 8 nm and 30 nm.

However, the treatment is preferably applied to glass substrates, on which is subsequently applied a thin opaque silver coating to form a mirror. Such embodiments of the present invention, wherein the product is a mirror, are used for example as domestic mirrors or as mirrors for vehicles. The present invention makes it possible to produce mirrors on which the silver coating has better adhesion to glass. Thus, according to another embodiment, the thickness of the layer of silver formed in said silvering step is between 70 nm and 100 nm.

According to the present invention, the glass activation is effected before silvering by treating the glass substrate with a specific solution activation. It is noted that the silver mirror coating produced in this way has a better grip than a mirror manufactured by the conventional method. Improved adhesion of the silver coating obtained by the process according to the present invention is seen in different ways. The adhesion of a silver coating to its glass substrate can be quickly established by test using adhesive tape: an adhesive tape is applied to the silver coating and then is pulled. If the silver lining is not firmly adhered to the glass, will come out of it when the tape is pulled. -6- The degree of adhesion of the silver coating to glass may also be observed by subjecting the product to an accelerated aging test such as the CASS test, or salt spray testing. There is sometimes the product subject to such testing has a certain degree of corrosion on their edges and / or points of light scattering ( "white spots"). The activation treatment according to the invention provides another advantage. It was observed that the silvering reaction on activated glass according to the invention is more effective, that is, the yield of the reaction is more effective. It is possible to obtain improvements in yield of about 15% compared with the effect of silvering on a glass activated in a conventional manner with ammoniacal silver nitrate solution. This provides advantages from an economic point of view, since they can employ a smaller quantity of reactants to form the same thickness of silver coating and also from the environmental point of view since the amount of waste to be eliminated from silvering reaction can be reduced. It is conventional to protect the silver coating with a copper over-coating to retard tarnishing of the silver layer. The copper layer is itself protected from abrasion and corrosion by a layer of paint. These ink formulations to produce the best protection against corrosion of the copper layer contain lead pigments. Unfortunately lead pigments are toxic and their use for environmental reasons, is being increasingly discouraged. -7-

It has recently been proposed to protect the silver coating by treatment with an acidified aqueous solution of Sn (II) salt (see British application GB Patent 2,252,568). According to another recent proposal, the silver coating is protected by treatment with a solution containing at least one of Cr (II), V (II or III), Ti (Π or III), Fe (II), In (I or II), Cu (I) and Al (III) (British patent application GB 2254339). It was observed that the activation treatment according to the present invention is particularly useful for the manufacture of such products. An important application of the protection treatments according to GB 2252568 and GB 2254339 is the formation of silver mirrors which do not include a conventional protective layer of copper. These mirrors can be protected with lead-free paints. The activation treatment according to the present invention is particularly advantageous for the manufacture of such mirrors. This is because the glass of the activation treatment for the manufacture of mirrors protected by such treatment significantly improves the adhesion of the silver coating such mirrors and so its durability. Accordingly, the invention applies preferably to the manufacture of mirrors with no copper layer, and particularly the mirrors formed by a process in which the silver coating is subsequently contacted with a solution containing ions of at least one of the group consisting of Cr (II), V (II or III), Ti (II or III), Fe (II), in (I or II), Sn (II), Cu (I) and AI (ΠΙ). The glass substrate may be brought into contact with the immersion activation solution in a tank containing an activating solution, but preferably, the glass substrate is brought into contact with the spray activating solution with a solution containing activation solution. This is -8

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particularly effective and practical in the case of flat glass substrates, for example during the industrial manufacture of flat mirrors, in which sheets of glass pass through successive stations where sensitization reagent, activation and then silvering are sprayed.

It was observed that the glass substrate can be effectively activated by a rapid treatment by using the specified activating solution. It was found that the contact time between the glass and the activation solution may be very short, for example around a few seconds only. In practice, the production of industrial flat mirrors, the sheet of glass moves along a mirror production line on which the glass passes through an activation station where the activating solution is sprayed, then through a washing station and then through the silvering station. The activation solution preferably comprises a source of palladium, most preferably palladium (II) salt in aqueous solution, in particular PdCl2 in an acidified aqueous solution. The activation solution may be employed very simple and cost. The PdCl2 solution may have a concentration between 5 and 130 mg / 1. We found that the glass substrate contacting with an amount between 1 and 23 mg, preferably at least 5 mg of PdCl2 per square meter of glass, are entirely sufficient to effectively activate the glass substrate. Indeed, we have observed that the use of PdCl2 in excess of 5 or 6 mg PdCl2 / m provides no significant improvement. -9-

Therefore, it is preferred to treat the glass substrate with about 5 to 6 mg of PdCl2 per square meter of glass.

We have found that the best results can be obtained when the pH of said activating solution ranges between 2.0 and 7.0, more preferably between 3.0 and 5.0. This pH range allows the formation of stable and effective solutions to the glass activation. For example, when employing palladium, at a pH below 3.0, the level thereof that is deposited on the glass substrate can be reduced, which leads to poor product quality. For a pH above 5.0 there is the risk of precipitation of palladium hydroxide.

According to a second aspect of the invention, there is provided a mirror comprising a glass substrate bearing a silver coating that is not coated with a copper protective layer, wherein the mirror has an average number of white points below 10 per dm2, preferably less than 5 per dm 2 after having been subjected to the CASS test of accelerated aging and / or Salt Fog test defined above. Such a silver mirror with no copper layer is advantageous, since the silver coating adheres well and has good durability. The silver coating may be covered with one or more protective paint layers and according to a preferred aspect of the invention, such an ink is substantially or completely free of lead. When employing more than one ink layer, the lower ink layers may contain lead. However, for reasons of environmental health, lead sulfate and lead carbonate are preferably disposed even in lower layers, so that, preferably, these lead layer is present only - 10-

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in the form of lead oxide. The present invention will now be described in greater detail in the following examples, by way of example only.

Example 1 + 1 control

The mirrors are manufactured on a conventional mirror production line in which the glass sheets are transported along that on a roller conveyor.

The glass sheets are first polished in total, they are washed and then sensitized by means of a tin chloride solution, in conventional manner, and then washed again.

An acidic aqueous solution of PdCl2 is then sprayed onto the sheets of glass. This solution is prepared from a solution containing 6 g of PdCl2 / acidified l with 1N HCl to give a pH of approximately 1, and diluted with demineralised water in order to be able to feed spray nozzles which direct the diluted solution which contains 60 mg PdCl2 / l, for the glass sheets so as to spray an amount of about 11 mg PdCl2 / m glass.

The sheets of glass thus activated then pass to a rinsing station where demineralised water is sprayed, and then to the silvering station where a traditional silvering solution is sprayed, comprising a silver salt and a reducing agent. This is achieved by simultaneously spraying a solution A containing ammoniacal silver nitrate and heptaglucónico acid and solution B containing ammoniacal sodium hydroxide. The flow rate and concentration of solution sprayed on the glass are controlled so as to form, under conventional production conditions, a layer containing approximately 800-850 mg / m of silver. It is observed that the mass of silver deposited is in supenor about 135 mg / m of silver, i.e. the total mass is about 935-985 mg / m2 of silver.

A copper solution with a normal composition is sprayed onto the silver coating in order to form a coating containing approximately 300 mg / m2 of copper. This is achieved by simultaneously spraying a solution A and a solution B. Solution A is prepared by mixing an ammonia solution with a solution containing copper sulphate and hydroxylamine sulphate. Solution B contains citric acid and sulfuric acid. The glass is then rinsed, is dried and covered with a Levis paint Epoxy. This paint comprises a first coat of approximately 25 .mu.m epoxy and a second coat of approximately 30 .mu.m alkyd. The mirrors are allowed to stand for 5 days to ensure complete curing of the paint layers.

Mirrors manufactured in this manner are subjected to various accelerated aging tests.

One indication of the resistance to aging of a mirror incorporating a metallic film can be given by subjecting it to a test of spraying an acetic acid salt accelerated copper known as the CASS Test in which the mirror is placed in a chamber test at 50 ° C and is subjected to the action of fog formed by spraying an aqueous solution containing 50 g / 1 sodium and 0.2 g / 1 anhydrous chloride - 12-

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cuprous with sufficient glacial acetic acid to bring the pH of the sprayed solution to a value between 3.0 and 3.1. The details of this assay are described in International Standard ISO 3770-1976. The mirrors are subjected to the action of saline fog for different lengths of time, after which the reflective properties of the artificially aged mirror is compared with the reflective properties of a mirror finished to manufacture. We have found that a 120 hour exposure time provides a useful indication of the resistance of a mirror to aging. We took out the CASS test in square mirror tiles, 10 cm edge and, after exposure for 120 hours to an accelerated acetic acid salt spray and copper, each tile is subjected to microscopic examination. The principal visible evidence of corrosion is a darkening of the silver layer and lifting of the paint film around the mirror edges. The extent of corrosion is recorded at five regularly spaced sites on each of two edges of the tile and the mean of these ten measurements is calculated. One can also measure the maximum corrosion present at the edges of the tile to obtain a result which is again measured in micrometers.

A second indication of the resistance to aging of a mirror incorporating a metallic film can be given by subjecting it to a spray test Salina, which comprises subjecting the mirror to the action, in a chamber maintained at 35 ° C, a haze salt formed by spraying an aqueous solution containing 50 g / 1 of sodium chloride. We find that an exposure time of 480 hours after the Salt Fog Test gives a useful indication of the resistance of a mirror to aging. The mirror is again subjected to microscopic examination, and the corrosion present at the margin of the tile is measured to obtain a result in micrometers, as in the CASS Test.

square mirrors with 10 cm edges made according to example 1 are subjected to the CASS test and salt spray, in parallel with control samples made by processes of the present invention.

These Control samples are manufactured from sheets of glass as described in Example 1, except that the activation step with PdCl2 followed by rinsing is omitted. This step is replaced by a traditional activation step, by spraying with an ammoniacal solution of silver nitrate.

The results of the two aging tests mirror of Example 1 and Control Sample 1 are shown in Table I below:

TABLE I

CASS test average pm Salt Fog Test μιτι average density of white spots average number / dm 2 Example 97 1334 Control 0 1480153 0

The mirrors according to Example 1 and Control 1 showed no white spots in the end of these two tests. - 14- The treatment consisting of the activation of the glass with palladium (II) chloride before silvering according to Example 1, reduced corrosion of the mirror edges, which shows an improved adhesion to silver compared with a mirror in which the glass was activated in a conventional manner with ammoniacal silver nitrate.

Examples 2 and 3 &amp; amp; Controls 2:03

Mirrors according to the invention are manufactured on a conventional mirror production line in which sheets of glass are conveyed by a roller conveyor.

The glass sheets are first polished, rinsed and then sensitized by means of a tin chloride solution, in the usual way, and then washed again.

An aqueous acidic solution of PdCl2 is then sprayed onto the sheets of glass. This solution is prepared from a starting solution containing 6 g of PdCl2 / acidified there with HC1, to provide a pH of approximately 1, and diluted with demineralised water in order to be able to feed spray nozzles which direct the dilute solution, which contains about 30 mg PdCl2 / l, for the glass sheets so as to spray an amount of approximately 5.5 mg of PdCl2 / m glass. The palladium chloride of contact time on the surface of the sensitized glass is approximately 15 seconds. - 15-

The sheets of glass thus activated then pass to a rinsing station where demineralised water is sprayed, and then to the silvering station where a traditional silvering solution is sprayed, comprising a silver salt and a reducing agent. The flow rate and concentration of solution sprayed onto the glass are controlled so as to form, under conventional production conditions, a layer containing approximately 800-850 mg / m of silver. It is observed that the mass of silver deposited is higher by about 100 mg / m2 of silver, that is, the total weight is about 900-950 mg / m2 of silver. The glass is then rinsed. Immediately after rinsing of the silver coating is sprayed onto an acidic solution of freshly tin chloride to about the glass sheets moving forward, as described in patent GB 2252568.

The mirrors are then treated by spraying with a solution containing 0.1% by volume of γ-aminopropyl triethoxysilane (Silane A 1100 from Union Carbide). After washing and drying, the mirrors are covered with a Levis paint. This paint comprises a first coat of approximately 25 .mu.m epoxy and a second coat of approximately 30 .mu.m alkyd (Example 2).

According to an embodiment (Example 3), the mirrors are coated not with a Levis paint, but with an ink that corresponds Merckens alkyd two layers with a total thickness of approximately 50 pm. The two coats of paint were specifically an undercoat of Merckens SK 8055 and the jacket was Merckens SK 7925. These two layers contain lead. The mirrors are allowed to stand for 5 days to ensure complete curing of the paint layers.

Mirrors manufactured in this way are subject to accelerated aging tests of CASS and salt spray.

Two control samples were not made according to the present invention are also subjected to the same tests.

These Control samples are manufactured from sheets of glass as described above, except that the activation step with PdCl2 followed by rinsing is omitted. This step is replaced by a traditional activation step consisting in spraying with an ammoniacal solution of silver nitrate.

The results of aging tests of Example mirrors 2 and 3 and samples of Control 2 and 3 are shown in the following Table II:

TABLE II

CASS test average prn Salt Fog Test μτη average density of white spots average number / dm 2 Example 30 2 140 0.7 Control 2170-110 20 to 50 Example 3 100 &amp; lt; Control 6 1.0 3130 58 20 50 the defect of "white spots" is observed after the two tests. This corresponds to a time when the silver coating begins to leave - 17- locally, accompanied by the formation of silver clusters, which appear as a point scattered light. These defects have a circular shape and the average size of 40 jim and 80pm. The value of 'density of white spots "given above is the average number of white dots per dm glass which are observed at the end of the salt spray and CASS tests. In fact, the number of white spots measured at the end of each of the two trials is usually very close to each other. This is probably because of this defect "white spots" appears when the mirrors are brought into contact with water (vapor or liquid phase). The test CASS and salt spray test consists in subjecting the mirror to the action of a fog saline solution: an aqueous NaCl solution in the case of salt spray, and a solution containing sodium chloride, copper chloride (I ) and acetic acid in the case of the CASS test. It is not surprising therefore that the number of white points after each test to be relatively similar. The treatment consists of glass activation with palladium (II) chloride before silvering according to Examples 2 and 3 reduces therefore the corrosion of the mirror edges, when compared with a mirror on which the glass has been activated in the conventional manner, ie with ammoniacal silver nitrate. Moreover, these mirrors according to Example 2 and 3 show a very significant decrease in the number of white points after the CASS test and salt spray. The adhesion of the silver to glass is so much larger when compared with mirrors in which the glass has been activated in the conventional way with silver nitrate. - 18-

Examples 4 5:06

The mirrors are manufactured as described in Example 2, by varying the quantity of palladium chloride is sprayed onto the glass. The starting solution containing 6 g of PdCl2 / l, with a pH of approximately 1, is diluted to vary the amounts in the distribution manifolds as follows:

Example 4: 12 mg of PdCl2 to afford 2.2 mg of PdCl2 per m2 of glass;

Example 5: about 30 mg PdCl2 / l to yield PdCl2 per square meter of glass; and

Example 6: 60 mg PdCl2 / l to yield 11 mg of PdCl2 per m2 of glass.

The results of the aging tests on these mirrors according to Examples 4, 5 and 6 are shown in Table III below:

TABLE III

CASS test average μτη Salt Fog Test average pm density of white spots average number / dm 2 Example 4 181 60 18 Example 5 166 16 1 Example 6 163 16 1 The defect of "white points" is observed only at end of test CASS. The number of "white spots" after the salt spray test was not measured.

It was observed however that the activation of the glass by spraying with 2.2 mg of PdCl2 per m2 of glass provides a mirror which resists - 19-

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aging tests relatively well. However, the density of white spots in the end of the CASS test decreases dramatically if pulverizarem 5.6 instead of 2.2 mg of PdCl2 / m glass. The spray large amounts of PdCl 2 (see Example 6: 11 mg PdCl2 / m2 glass) does not provide any significant improvement.

Examples 7 to 11 and Control 4

Mirrors are formed as described in Example 3, by varying the amount of palladium chloride is sprayed onto the glass. Initially, the solution containing 6 g of PdCl2 / l at pH 1. This solution is diluted as indicated in the following Table IV:

EXAMPLE TABLE IV Solution mg PdCl2 / l spray Level mg of PdCl2 / ni LI 6 Example 7 Example 8 Example 9 2.2 12 30 5.5 10 60 Example 11 11 120 Example 22

The mirrors were formed in this way were subjected to the CASS test and salt spray. At the same time, a control sample not made according to the present invention was subjected to the same tests. The control sample was made from glass plates as described in Example 3 except that the activation step with PdCl2 was omitted. This step -20-

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It was replaced by a normal activation step, or by spraying with ammoniacal silver nitrate. The observation of the "white spots" is made after the CASS test and after the Salt Fog test. The results are shown in Tables Va and Vb. TABLE Va EXAMPLE CASS test average pm White 2 Average points / dm Control 4124 47 Example 7254 40 Example 8156 24 Example 9101 3 Example 10 102 3 Example 11 129 2 TABLE Vb EXAMPLE Salt Fog test average pm Points white 2 average / dm Control 4 41 10 Example 7 87 Example 8 41 Example 9 13 52 7 1 Example 10 13 Example 11 5 1 1 from these results it can be seen that activation of the glass by spraying 1.1 or 2 2 mg PdCl2 / m2 glass results in -21 -

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mirror that resists aging tests relatively well. Furthermore, the density of white spots in the end of the CASS test becomes very low PdCl2 if the level is increased to 5.5 mg / m glass. High levels of PdCl2 (for example as employed in Examples 10 and 11) do not lead to a significant improvement.

Examples 12 to 15 and Control 5

The mirrors are manufactured as described in Example 3 with the following variations:

Example 12 About 6 mg PdCl2 / m2 is sprayed onto glass, instead of 5.5 mg of PdCl2 / m2. The amount of PdCl2 is also increased to about 6 mg PdCl2 / m 2 glass in Examples 13 to 15.

Example 13: The sensitization step with tin chloride is omitted.

Example 14: The activation step with PdCl2 is performed before the sensitization step with tin chloride.

Example 15: The protection step of the silver coating by treatment with a freshly formed acidified solution of tin chloride was not performed. The silver glass plates were coated directly with Merckens ink. -22-

Control 5: Mirror not manufactured according to the invention were produced as described in Example 12, except that the activation step with PdCl2 followed by rinsing was replaced by a traditional activation step, i.e. by spraying an ammoniacal solution silver nitrate.

The mirrors made according to Examples 12 to 15 and Control 5 were subjected to an accelerated CASS aging test. The corrosion of the edges and the density of white dots at the end of this test are shown in Table Via: TABLE Via EXAMPLE CASS test average μτη white average points / dm2 Control 5395 32 Example 12 165 2 Example 13 2700 * Example 14 650 46 example 15 3200 55 * the silver coating was so destroyed at the glass interface / silver which was not possible to identify the white dots.

Mirrors manufactured in accordance with Examples 12, 13, 14 and 15, and the control 5 are subjected to the salt spray test. The corrosion of the edges and the density of white dots at the end of the Salt Fog test were as shown in Table VIb following: -23 - Table VIb EXAMPLE Mist test Salina pm average white average points / dm2 Control 5 70 47 Example 12 41 * Example 2 13 760 Example 14 93 Example 46 15 132 &amp; gt; 125 * The silver coating was so destroyed at the glass interface / silver which was not possible to identify the white dots.

It can be seen by comparing the results of Examples 12 and 13, it is important to sensitize the glass before activation with PdCl2. The order of the steps of awareness and activation is very important: when activation is performed before sensitization, are obtained worse aging results (see Example 14). Example 15 shows that it is important to protect the silver coating prior to painting.

Examples 16 to 21

Mirrors are manufactured in the manner described in Example 2, except that the activating solution is poured into the glass, rather than being sprayed thereon. Pour 500 ml of an acidified solution over 0.5 m glass. The contact time of the solution on the surface of the sensitized glass -24-

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is approximately 30 seconds. We used the following activation solutions:

Example 16: an acidified aqueous solution which contained 6 mg / 1 PdCl2. The pH was 3.8.

Example 17: an acidified aqueous solution containing 10.0 mg / 1 AuC13 (pH = 4.1).

Example 18: an acidified aqueous solution containing 10.2 mg / 1 PtCl2 (pH = 4.0).

Example 19: an acidified aqueous solution containing 6.7 mg / 1 RuC13 (pH = 4.0).

Example 20: an acidified aqueous solution which contained 8 mg l / 1 NiCl2-6H20 (pH - 4.3).

Example 21: an acidified aqueous solution containing 3.6 mg / l CrCl2 (pH = 4.2).

Mirrors manufactured in Examples 16 to 21 were subjected to an accelerated CASS aging test. The corrosion of the edges and the density of white dots at the end of this test are given in TABLES Vila and VIIb: TABLE Vila EXAMPLE CASS test average | im white average points / dm2 Control 61 477 0 16 (PdCl2) 143 7 17 (AuClO 262 55 18 (PtCl 2) 204 * 19 (RuCli) 187 8 20 (NiCl, -6H20) 298 34 21 (CrCl2) 180 TABLE 3 EXAMPLE VIIb Salt Fog test pm average white average points / dm2 Control 6214 16 0 ( PdCl2) 53 5 17 (AuCM 117 73 18 (PtCl2) 107 * 19 (53 RuClO 6 20 (NiCI2-6H20) 82 46 21 (CrCl2) __ 39 10 the Control # 6 is a mirror similar to Control 1, that is , is a silver mirror manufactured in the traditional manner and supports a coating of copper to protect the silver layer. the first surface of the silver coating showed a number of aligned faults indicating separation of the silver. -26-

It can be seen that all the salts used in the activation of the solutions used in Examples 16 to 21 give better results from the point of view of marginal corrosion after the test CASS compared with those obtained with mirrors produced in the traditional way, according to which a copper coating is applied. Best results were obtained with PdCl2 (II), Cr (II) and Ru (III).

Examples 22 to 24 Example 3 was followed, except that in Example 22 the two layers of paint have specifically been an undercoat of Merckens SK9085 (a paint containing lead, which is in the form of lead oxide) and jacket Merckens SK8950 (lead free). The results were compared with a modification (Example 23), in which the undercoat was Merckens SK9135 (a paint containing lead, which is present as an oxide) and the jacket was Merckens SK8950 (lead-free ) and with a second modification (Example 24), in which the undercoat was Merckens SK8055 (a paint containing lead which is present in the form of carbonate, sulfate, and oxide) and the over-cover was Merckens SK8950 . The results of these tests on the products obtained are shown in TABLE VIIIa and VIIIb: TABLE VIIIa EXAMPLE CASS test average pm white average points / dm 2 Example 22 164 1 Example 23 85 0 Example 24 118 2 TABLE VIIIb EXAMPLE Test of Salt Fog average pm average white spots / dm 2 Example 22 19 0.5 Example 23 22 Example 24 0 22 0.5

Examples 25 to 27 The procedure of Example 2 was followed, except that the activating solution was acidified with different amounts of hydrochloric acid to produce diluted solutions (ie, solutions sprayed on glass) with different pHs. Samples were assayed by the CASS test and salt fog by the test and were also analyzed to determine the level of palladium deposited on the substrate in the activation step. In the following tables of results (TABLES IXa and IXb), palladium level is expressed as the relationship with silicon. The presence of these palladium atoms, and its ratio to the silicon atoms present in the glass can be estimated by a bombardment technique which causes the ejection of electrons from a layer of glass surface. From the energy of the beam of X-rays and the energy of the emitted electrons, it is possible to calculate the binding energy of the electrons so that they can be divided between specific layers of electrons of different atomic species. The atomic ratios of palladium and silicon can be calculated quickly. This analysis is generally performed on the activated glass before silvering and painting. The presence of palladium (or other atom according to the type of activation solution -28- used) can also be analyzed by Secondary Ion Mass Spectroscopy. TABLE IXa

Example Activator (pH ± 0.5) Pd ratio / Si CASS test average jim white points 2 Average / dm Example 25 PdCl2 (3.5) 0.12 71 0 Example 26 PdCl, (4.5) 0.16 1 65 Example 27 PdCl2 (2.5) 0.03 76 2 TABLE IXb

Example Activator (pH ± 0.5) ratio Pd / Si Salt Fog test pm average white average points / dm2 Example 25 PdCl2 (3.5) 0.12 15 0.5 Example 26 PdCl2 (4.5) 0, 0 16 18 Example 27 PdCl2 (2.5) 0.03 76 9

These results show that the pH is low, the palladium level set on the substrate is low and the results are worse. If the pH exceeds 5, you can obtain a palladium hydroxide precipitate which can result in the locking device.

Examples 28 to 43

Employing the procedure described for Examples 16 through 21 used a series of activating solutions as follows. -29-

Example 28: acidified aqueous solution containing 10.7 mg / 1 AuC13 (pH = 4.6).

Example 29: acidified aqueous solution containing 5.9 mg / 1 PtCl2 (pH = 3.5).

Example 30: acidified aqueous solution containing 8.2 mg / 1 NiCl2-6H20 (pH = 4.6).

Example 31: acidified aqueous solution containing 5.9 mg / 1 PdCl2 (pH = 4.6).

Example 32: acidified aqueous solution containing 5.9 mg / 1 PdCl2 (pH = 4.1).

Example 33: acidified aqueous solution containing 8.3 mg / 1 InCl3 (pH = 4.6).

Example 34: acidified aqueous solution containing 8.3 mg / 1 InCl3 (pH = 4, L).

Example 35: acidified aqueous solution containing 4.4 mg / 1 of ZnCl2 (pH = 4.6).

Example 36: acidified aqueous solution containing 4.4 mg / 1 of ZnCl2 (pH = 4, L). -30-

Example 37: acidified aqueous solution containing 54.6 mg / 1 of BiCl3 (pH = 4.6). Note that 0 BiCl3 is only slightly soluble.

Example 38: acidified aqueous solution containing 54.6 mg / 1 of BiCl3 (pH = 3.5).

Example 39: acidified aqueous solution containing 7.8 mg / 1 RhCl3-3H20 (pH = 4.6).

Example 40: acidified aqueous solution containing 7.8 mg / 1 RhCl3-3H20 (pH = 4, L).

Example 41: acidified aqueous solution containing 5.4 mg / 1 of VC13 (pH = 4.6).

Example 42: acidified aqueous solution containing 5.4 mg / 1 of VC13 (pH = 4, L).

Example 43: acidified aqueous solution containing 5.8 mg / 1 of TiCl3 (pH = 4.5).

The mirrors were subjected to the CASS test. Some relationships metal / silicon were estimated on activated glass. The results were as follows: -31 -

TABLE X

Example No. CASS test average white pm average points / dm2 ratio Me / Si 28 (AuCl3 pH = 4.6) 219 1 0.03 29 (PtCl 2 pH = 3.5) 131 20 0,007 30 (NiCl2.6H2O pH = 4.6) 144 19 0.028 31 (PdCl2 pH = 4.6) 161 1.5 0.032 32 (PdCl2 pH = 4, l) 0 0.076 106 33 (InCl3 pH = 4.6) 127 3 34 (InCl3 pH = 4 l) 10 0.045 123 35 (ZnCl2 pH = 4.6) 141 9. 36 (ZnCl2 pH = 4.1) 126 11 0.006 37 (BiCl3 pH = 4.6) 155 11 38 (BiCl3 pH = 3.5 ) 180 13 39 (RhCl3.3H20 pH = 4.6) 149 29 40 (RhCU.3H2O pH = 4.1) 167 8.5 0.016 41 (VCl3 pH = 4.6) 164 2 42 (VCl3 pH = 4, 1) 179 4.5 0.014 43 (TiCl3 pH = 4.5) 256 0.012 33.5

The best results are obtained with the use of AuC13, PdCl 2, InCl 3, VCI3: the mirrors exhibit an average number of white spots of less than 5 per dm. With ZnCl2 or RhCl3.3H20, mirrors had an average number of white spots between 5 and 10 per dm.

Lisbon, May 9, 1995

<img img-format="tif" img-content="drawing" file="PT-101700-BD00331.tif" id="idf0010" />

JORGE CRUZ

Industrial Property Official Agent STREET VICTOR CORDON, 10 - The 3 "1200 USBOA