Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1999-08-11
2002-05-14
Turner, Archene (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C501S017000, C501S019000, C501S020000, C501S021000, C427S164000, C427S165000, C427S167000, C427S396000, C428S426000, C428S427000, C428S469000, C428S472000
Reexamination Certificate
active
06387513
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the deposition of enamel on a glass substrate, in particular on a glazing. It relates in particular to a novel enamel composition and to a novel process for the manufacture of an enamelled layer on a glass substrate, as well as to the enamelled products obtained.
Enamels are well known in the prior art and are used, in particular, for coating glass substrates, such as window panes, in the motor-vehicle industry or the building industry. They make it possible, inter alia, to form inscriptions or decorative layers, conductive layers, protective layers, in particular layers for protecting against ultraviolet radiation the adhesive layers or adhesive beads intended for fitting the window panes into bodywork openings, masks, in particular masks for concealing current-collecting strips of heater arrays or for concealing the adhesive beads mentioned above, etc.
The enamels used for coating glass substrates are generally formed (before they are applied to the substrate and fired) from a powder which includes a glass frit (which has to form the glassy matrix), and from pigments (in particular as colorants, it being possible for these pigments also to form part of the frit), the frit and the pigments being based on metal oxides, and from a medium or “vehicle” allowing application and temporary adhesion of the enamel to a substrate. The vehicle, chosen depending on the end-use of the enamel, must ensure that the particles of the frits and pigments used are properly in suspension and must be consumed at the latest during firing of the enamel. This vehicle may contain solvents, diluents, oils, resins, etc.
One problem with existing enamelled glass substrates is the difficulty of recycling such products, in particular in the manufacture of glass substrates in the form of sheets (glazings). Since glazings have to satisfy many requirements in terms of coloration, light and/or energy transmission, etc., it is indeed important for glass waste reintroduced in ground form (cullet) into the melting furnaces used for manufacturing glazings not to disturb the usually already present glass compositions and not to give products which do not meet the necessary requirements. Although non-enamelled glass cullet may thus be reintroduced into a furnace for manufacturing float glass, in amounts generally of about 20-30% by weight of the furnace charge, enamelled glass cullet, on the other hand, generally results in the appearance of undesirable residual colorations or non-melted islands in the glass sheets formed. The amount of enamelled glass cullet which can be reintroduced into these furnaces consequently does not exceed, in the most favorable cases, from 2 to 3% by weight of the charge of the furnaces (the enamel generally constituting from 0.1 to 0.5% by weight of this glass cullet).
SUMMARY OF THE INVENTION
The object of the present invention is to provide an improved enamel composition and an enamelling process making it possible to obtain improved enamelled glass substrates (especially glazings), in particular enamelled substrates which can be more easily recycled (in particular in the manufacture of glazings) than the existing enamelled substrates, the enamelled layers obtained furthermore preferably having the usually required characteristics (in particular, in terms of opacity and coloration) for the enamelled layers which have to coat window panes (glazings) for motor vehicles.
This object is achieved by the enamel composition according to the invention, this composition including at least one glass frit and including, as pigment(s), at least one or more manganese compounds, this composition furthermore having a melting temperature below 750° C.
DETAILED DESCRIPTION OF THE INVENTION
In one advantageous embodiment of the invention, the enamel composition furthermore includes less than 10% by weight (with respect to the composition) and, preferably, less than 5% by weight of silver particles.
Particularly preferably, it includes less than 10% and advantageously less than 5% by weight of silver particles and of any other silver-based compound and/or includes less than 10% and advantageously less than 5% by weight of silver particles and of any other conductive particle (i.e., in the latter case, it includes less than 10% and advantageously less than 5% of conductive particles). In particular, the compositions according to the invention containing no silver particles and/or no silver-based compounds and/or no other conductive particles and/or no certain undesirable heavy metals mentioned later (in particular, lead or lead oxides) have many advantages, as will be explained later.
The expression “enamel composition” is understood to mean, according to the invention, the composition of the enamel considered before it is fired, the enamel after it has been fired being essentially in the form of a coloured glassy matrix. The expression “melting temperature of the enamel composition” is understood to mean, according to the invention, the melting temperature of the enamel in its form as deposited on the substrate to be coated. This “melting temperature” is also commonly called “firing temperature” or “fusability temperature”. In the field of enamels, it corresponds to the minimum temperature at which “sufficient” sintering of the composition is observed, this “sufficient” sintering being manifested in particular by the disappearance of the capillary effect in the enamel during sintering. Those skilled in the art know how to measure this melting temperature, for example by passing an ink pen (i.e. more specifically a felt-tip pen) over the enamel (after the latter has been raised to a treatment temperature and then cooled) and by noting the lowest treatment temperature for which the trace, left through the cooled enamel by the solvents in the ink when they are absorbed by the enamel due to the capillary effect, disappears. During the production of an enamelled substrate, the temperature chosen for firing the enamel deposited on the substrate is then preferably chosen to be above or equal to its melting temperature. As a general rule, and preferably, the melting temperature of the enamel composition according to the invention is below 700° C.
According to the invention, the enamel composition includes at least one or more manganese compounds (this is generally a single compound, but it may also be a mixture of various manganese compounds) as pigment(s). Preferably it includes the said manganese compound(s) as the main pigment(s), that is to say that the enamel composition may optionally include one or more other pigments but that, in this case, the amount of each other optional pigment remains less than the amount of manganese compound(s). Particularly advantageously (in particular, for reasons associated with recycling), the manganese compound(s) represents (represent) at least 50% by weight of the pigments present, preferably at least 75% by weight of the pigments present, and is (are) particularly preferably the only pigment(s) used in the composition according to the invention. In particular, the enamel composition according to the invention advantageously contains no chromium oxides, no copper oxides, no cobalt oxides or nickel oxides and also contains no other colorant compounds, such as copper chromates, cobalt chromates, etc. and/or no other colorant oxides, such as iron oxides, etc.
The manganese compound(s) is (are) preferably added in the form of manganese salt (or salts) and/or of manganese oxide(s) (for example, MnO
2
and/or Mn
2
O
3
and/or Mn
3
O
4
and/or MnO) to the enamel composition according to the invention, particularly preferably in the form of manganese carbonate(s) and/or MnO
2
. Depending on the way in which the enamel composition is prepared, it (they) may also be provided or occur in another form (or other forms) in the composition (in particular, in the form of other manganese derivatives). As a general rule, it (they) gives (give) one or more manganese oxides (preferably, Mn
3
O
4
optionally accompanied by Mn
2
O
3
Beyrle Andre
Dages Daniel
DeJean Aline
Veret-Lemarinier Anne-Valentine
Pennie & Edmonds LLP
Saint Gobain Vitrage
Turner Archene
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