GLAZING PROVIDED WITH A TEMPORARY PROTECTIVE LAYER AND WITH A PRINTED LOGO OR PATTERN

Abstract

A glass substrate includes on a face a water-insoluble polymeric temporary protective layer intended to be removed by heat treatment during a processing operation, and an enamel layer that has a mixture of glass frit, inorganic pigments and organic components that is deposited on at least one portion of the protective layer. The enamel has a glass transition temperature Tg above the temperature Tc.sub.60%, defined as being the temperature at which 60% of the initial weight of the protective layer is consumed, a maximum shrinkage measured by thermomechanical analysis between 450 C. and 650 C. greater than 20%, a difference between the inflection point temperature T.sub.inflection and the glass transition temperature Tg less than 60 C., the inflection point temperature being defined as being the temperature at which the rate of displacement measured by thermomechanical analysis of the enamel is maximum, and a content of inorganic pigments less than 35% by weight.

Claims

1. A glass or glass-ceramic substrate comprising, on at least one portion of one of its faces: a water-insoluble polymeric temporary protective layer intended to be removed by heat treatment during a processing operation of the substrate, and an enamel layer consisting of a mixture of glass frit, inorganic pigments and organic components that is deposited on at least one portion of the water-insoluble polymeric temporary protective layer, said enamel having: a glass transition temperature Tg that is above the temperature Tc.sub.60%, defined as being the temperature at which 60% of the initial weight of the protective layer is consumed, said temperature Tc.sub.60% being determined by thermogravimetric analysis in air, a maximum shrinkage measured by thermomechanical analysis between 450 C. and 650 C. that is greater than 20%, a difference between the inflection point temperature T.sub.inflection and the glass transition temperature Tg that is less than 60 C., the inflection point temperature being defined as being the temperature at which the rate of displacement measured by thermomechanical analysis of the enamel is maximum, and a content of inorganic pigments incorporated into a total composition of the enamel that is less than 35% by weight.

2. The substrate as claimed in claim 1, wherein the glass transition temperature Tg of the enamel is above the temperature Tc.sub.75%, defined as being the temperature at which 75% of the initial weight of the protective layer is consumed, Tc.sub.75% being determined by thermogravimetric analysis in air.

3. The substrate as claimed in claim 1, wherein the glass transition temperature Tg of the enamel is above the temperature Tc.sub.85%, defined as being the temperature at which 85% of the initial weight of the protective layer is consumed, Tc.sub.85% being determined by thermogravimetric analysis in air.

4. The substrate as claimed in claim 1, wherein the enamel is densified over a temperature range such that the temperature difference between T.sub.inflection and the glass transition temperature Tg is less than or equal to 50 C.

5. The substrate as claimed in claim 1, wherein the enamel layer comprises less than 20% by weight of pigments relative to the total composition of the enamel.

6. The substrate as claimed in claim 1, wherein the enamel layer comprises less than 45% by weight of organic components relative to the total composition of the enamel.

7. The substrate as claimed in claim 1, wherein the temporary protective layer is obtained by curing a liquid composition comprising (meth)acrylate compounds.

8. The substrate as claimed in claim 7, wherein the liquid composition that makes it possible to obtain the polymeric layer comprises an aliphatic urethane-acrylic oligomer, a mono-, di- and/or tri-functional (meth)acrylate monomer and a polymerization initiator.

9. The substrate as claimed in claim 7, wherein the thickness of the water-insoluble polymeric temporary protective layer is between 1 and 30 m.

10. The substrate as claimed in claim 9, wherein the thickness of the water-insoluble polymeric temporary protective layer is between 5 and 20 m.

11. The substrate as claimed in claim 1, further comprising a functional coating on the glass or the glass-ceramic, underneath the water-insoluble polymeric temporary protective layer.

12. The substrate as claimed in claim 1, wherein the enamel layer forms a logo or a pattern.

13. A process for manufacturing a glass or glass-ceramic substrate on which a logo or pattern is printed, comprising heat treating, at a temperature above 400 C., the substrate as claimed in claim 1.

14. The process as claimed in claim 13, wherein the heat treatment is a tempering.

15. The substrate as claimed in claim 1, wherein the processing operation of the substrate is an annealing, a bending and/or a tempering.

16. The substrate as claimed in claim 6, wherein the enamel layer comprises less than 35% by weight of organic components relative to the total composition of the enamel.

17. The substrate as claimed in claim 16, wherein the enamel layer comprises less than 30% by weight of organic components relative to the total composition of the enamel.

18. The substrate as claimed in claim 9, wherein the thickness of the water-insoluble polymeric temporary protective layer is between 2 and 25 m.

Description

[0035] The present invention also relates to a process for manufacturing a glass or glass-ceramic substrate on which a logo or pattern is printed, comprising a step of heat treatment, at a temperature above 400 C., of the substrate as described above.

[0036] The heat treatment is preferably a tempering.

[0037] The examples below illustrate the invention without limiting the scope thereof.

[0038] The glass substrates used below are glass substrates of around 6 mm thick obtained by a float process that consists in pouring the molten glass onto a bath of tin.

[0039] A protective polymeric film is obtained by curing a liquid composition based on oligomers and monomers comprising at least one acrylate function, sold by the company Sartomer. The liquid composition is a mixture of CN9276 (tetrafunctional aliphatic urethane-acrylate oligomer), SR351 (trimethylolpropane triacrylate), and SR833S (tricyclodecane dimethanol diacrylate) and is described in application FR3009302. This film deposited on the glass substrate corresponds to the temporary protective layer. A thermogravimetric analysis (TGA) of this film is carried out by placing 2 mg of polymer scraped off the surface of a glass substrate covered with the polymeric film into a platinum crucible. The sample is placed in the analyzer (TGA Q50 from TA Instrument) under an air flow of 60 ml/min and is heated between 20 C. and 600 C., by increasing the temperature by 10 C./min. The analyzer measures the weight variation of the sample as a function of the temperature. The curve obtained is given in FIG. 1. It is noted that the initial combustion temperature Tci of this polymeric layer is 295 C.

[0040] The temperatures Tc.sub.60%, Tc.sub.75% and Tc.sub.85% of the polymeric film constituting the temporary protective layer are respectively equal to 400 C., 465 C. and 510 C.

[0041] Screen printing tests were carried out using various enamels (enamels 1 to 6), the features of which are given below. The enamels 1 (enamel 194020 from the company Ferro), 2 (enamel DV775370 from the company PMI), 5, and 6 (enamel 194011 from the company Ferro) contain zinc borosilicate frits and the enamels 3 (enamel 194120 from the company Ferro) and 4 contain bismuth borosilicate frits.

[0042] The analyses carried out on the enamels are the following: [0043] thermomechanical analysis (TMA) with a TMA4000 analyzer from Perkin Elmer, [0044] thermogravimetric analysis (TGA) with a Q50 analyzer from TA Instrument to determine the content of organic components of the enamel, [0045] x-ray fluorescence to determine the total weight percentage of pigment in the enamel composition, carried out with a PANalytical Axios analyzer.

[0046] For the thermomechanical analysis, a sample of powdered enamel is prepared in the form of a 25 mg pellet. The organic constituents (organic medium) of the enamel were previously dried and burnt off in a radiative furnace at 450 C. The pellets are prepared in a hydraulic press under 4 N of pressure in a 6 mm diameter cylinder. The pellet is then placed in the analyzer between two 6 mm diameter quartz disks with a height of 1 mm. The temperature is then increased from 20 C. to 650 C. at a rate of 10 C./min under a constant pressure of 0.1 N applied to the sample. The curve representing the measurement of displacement (in mm) as a function of the temperature and also the first-order derivative of this curve are given in FIG. 2 for enamel 1. It is deduced from these curves that the glass transition temperature of enamel 1 is equal to 518 C. and that the temperature T.sub.inflection at which the rate of displacement is maximum is equal to 559 C. The variations in the shrinkage of the enamel as a function of the temperature may also be measured from this analysis. The curves of variation in the shrinkage as a function of the temperature that are obtained for the various enamels tested are given in FIG. 3.

[0047] The characteristic temperatures of the various enamels tested are grouped together in the table below:

TABLE-US-00001 Enamel Enamel Enamel Enamel Enamel Enamel 1 2 3 4 5 6 Tg ( C.) 518 527 505 496 532 533 T.sub.inflection ( C.) 559 571 549 560 598 575 T.sub.inflection Tg 41 44 44 64 66 42 ( C.) maximum 33% 49% 10% 35% 23% 13% shrinkage in % (measured between 450 C. and 650 C.) % by weight of 7% 9% 4% 3% 37% 40% inorganic pigments in the composition of the enamel

[0048] Enamels 1 to 6 have a content of organic components of less than 45% by weight relative to the total composition of the enamel.

[0049] A layer of each of the various enamels is deposited by screen printing on the substrates coated with the protective polymeric layer described above.

[0050] The samples below were produced by depositing enamel by screen printing in an air-conditioned room, using a screen with a mesh of 77.55 and a squeegee with a Shore hardness of 65. The enamels were mixed and brought to a viscosity of 15 Pa.Math.s at 20 C. upstream of the deposition. The samples thus enameled are dried in an IR dryer brought to a set point of 160 C. before undergoing a tempering heat treatment in a radiative and convective furnace at 690 C. The enameled patterns are printed onto the glass substrate in the form of a strip of around 17 mm and a square with sides of around 6 mm.

[0051] The products are then analyzed once the enamel is fired, therefore after having undergone a tempering treatment at a temperature of 690 during which the temporary protective polymeric layer is consumed and the enameled pattern is attached to the glass substrate. Photos taken face-on of each of the samples are given in FIG. 4. The photos obtained for the samples with enamels 1 to 4 remain identical before and after passing a dry cloth over the printed logo, unlike what is observed for the sample obtained with enamels 5 and 6.

[0052] The samples that respectively comprise the enamel 1 or 2 are in accordance with the invention whereas those that comprise one of the enamels 3 to 6 are given by way of comparison. The samples comprising the enamels 1 and 2 have both a good adhesion of the enamel and a good readability of the logo.

[0053] On the other hand, the samples comprising the enamels 3 to 6 do not give satisfactory results. Enamel 3 has too small a shrinkage, which leads to a heterogeneous sintering. Enamel 4 has a temperature T.sub.inflection that is too far away from its glass transition temperature Tg (T.sub.inflectionT.sub.g of 64 C.). Its densification is too slow, the sintering taking place too rapidly. Enamels 3 and 4 additionally have a glass transition temperature close to the combustion of the protective polymeric layer: the softening of the glass frit incorporated into their composition and their densification take place while the temporary protective polymeric layer is not yet sufficiently consumed. This results in particular in the appearance of bubbles in the enamel layer. Residues of unburnt organic matter originating from the polymeric layer are interposed between the glass substrate and the densified enamel, leading to a poor adhesion thereof.

[0054] Enamel 5 given by way of comparison has both a large amount of inorganic pigments in its composition (37% by weight relative to the total composition) and also a temperature T.sub.inflection that is too far away from its glass transition temperature Tg (T.sub.inflectionT.sub.g of 66 C.). This enamel has slow kinetics of shrinkage and therefore of densification and a sintering which takes place too late relative to its firing cycle. The presence of a large amount of pigments incorporated into the composition of the enamel disturbs the attachment of the glass frit on the substrate and results in a poor adhesion of the enamel layer.

[0055] Enamel 6, also given by way of comparison, also has too large an amount of pigments (40%), and also too low a shrinkage. The adhesion to the substrate is very poor.