METHOD OF PRINTING ON GLASS FOR DOUBLE VIEWING AND HIGH MELTING POINT INK USED IN SAID METHOD

Abstract

Method of printing on glass for double vision and high melting point ink used in said method. Method comprising the following stages: - printing a negative design with a high melting point ink >800 ºC forming a mask (1) that has a series of gaps (5), - printing of first surfaces on the gaps (5) of the mask (1) with a first ink with a first color, - printing of second surfaces on the first surfaces with a second ink, with a second color. - final drying - vitrified - removal of all printed inks on the mask (1) that have fallen onto the high melting point ink. High melting point ink comprises materials or oxides with a high melting point >800 degrees such as silica, zirconium oxide, magnesium oxide, beryllium oxide, and aluminum oxide.

Description

DOUBLE-VIEWING GLASS PRINTING METHOD AND INK HIGH MELTING POINT USED IN THIS METHOD OBJECT OF THE INVENTION The object of the present invention, as stated in the title of the invention, is, on the one hand, a method of printing on glass for double vision, and, on the other hand, a high melting point ink used in the above method. When we refer to a double-vision glass, we mean that on one side of the glass you see one design, while on the other side you see a completely different one. The present invention is characterized by the special design of the stages of the method, as well as the high melting point ink used in said method, so that it allows a glass to be obtained that allows different designs to be seen on each of its faces. Therefore, the present invention falls within the scope of digital printing on glass. BACKGROUND OF THE INVENTION Ceramic inks for digital printing on glass are already well-established in the art. These inks have proven to be of great help in glass processing for sectors such as automotive, architecture, and household appliances, among others. Thanks to these inks, the flexibility of printing on glass has been significantly improved, leaving behind traditional application techniques, such as screen printing, which required the use of printing screens for each model to be printed. This limited its use to large-scale production runs or made the product very expensive for very small print runs, since a single screen was used for only a few glass pieces, with the associated costs and the considerable time required to set up the machine for printing just a few pieces. Digital printing machines and the inks for them, already known in the state of the art, have contributed significantly to improving the limitations of traditional printing methods, as explained above. In digital printing on glass to achieve double vision glass, these prints are made with patterns of dots (positive or negative) or lines with a certain density to allow the desired amount of light to pass through. What currently happens is that, due to the mechanical tolerances of the printing presses and also the firing tolerance of the print heads themselves, there is a slight misalignment in the overlap of the printed areas. This misalignment means that (taking the simplest example of 1mm white dots overlapping 1mm black dots) when the glass is viewed from the side where only white dots should be visible, halos of the black dot are seen, which may be displaced to either side of the dot to a greater or lesser degree depending on the printing tolerance. The current printing method for double vision glasses comprises the following stages: - Printing a one-color design, for example, 1 mm white dots at 70% density - Intermediate drying (this step is optional) - Printing the same design superimposed on the first one, for example, black dots - Final drying - Vitrified. After vitrification, the two inks fuse with the glass, resulting in a white dot visible on one side and a black dot on the other. This method already explains the aesthetic problems that arise due to the tolerances involved, and therefore its limitations in use. The visibility from one side of halos or borders of the color that should be seen from the other side greatly limits the possibilities of using these designs, since it is not aesthetically acceptable and greatly slows down manufacturing because the rejection rate for selecting the glass with the minimum displacement of the designs is high. Therefore, the object of the present invention is to develop a printing method that overcomes the drawbacks of the methods used in digital printing of glass to achieve double vision glass, developing a method and an ink with a high melting point as described below and included in their essential aspects in claim one. DESCRIPTION OF THE INVENTION The object of the present invention is set out in its essentials in the independent claim and the different embodiments are set out in the dependent claims. The present invention relates to a method of printing on glass for double-vision glass, using an additional printing of an ink with a high melting point where this ink acts as a mask, thus ensuring that the prints are perfectly superimposed, avoiding these undesirable effects of seeing remnants of one of the prints on the side that should not be seen. The stages of the method now proposed are: - Printing a negative design to the desired final design with the ink also subject to this patent with a high melting point >800°C, for example, a design of negative dots of 1 mm at 70% density - Intermediate drying (this step is optional) - Printing of positive dots larger than the desired size (for example, in this case the desired size is 1 mm, therefore the design must be larger than 1 mm, for example 1.1 mm) in white - Intermediate drying (this step is optional) - Printing of positive dots larger than the desired size (for example, in this case the desired size is 1 mm, therefore the design must be larger than 1 mm, for example 1.1 mm) in black - Final drying - Vitrification. After vitrification, the two white and black printed inks superimposed in the space left by the high melting point ink will be fused onto the glass. - Removal of all white and black ink that may have fallen onto the high melting point ink, either due to the excess size already described and due to mechanical and firing tolerances, after a washing process with pressurized water or any other known washing method since the high melting point ink will not have melted onto the glass and will have prevented any remaining ink that does melt from melting onto the glass by creating a barrier. In the printing of the negative, an ink made with materials or oxides with a high melting point will be used, for example, at a temperature greater than 800ºC, such as silica, zirconium oxide, magnesium oxide, beryllium oxide, aluminum oxide. The use of inks with a high melting point aims to ensure that they are inks that do not melt onto the glass so that they can be easily removed by washing. After this washing, the two prints will be perfectly overlapped with a minimal tolerance that makes the product aesthetically acceptable and industrially manufacturable. Unless otherwise stated, all technical and scientific terms used herein have the meanings commonly understood by a person skilled in the art to which this invention pertains. Similar or equivalent procedures and materials to those described herein may be used in the practice of this invention. Throughout the description and claims, the word "comprises" and its variants are not intended to exclude other technical features, additives, components, or steps. For those skilled in the art, other objects, advantages, and features of the invention will become apparent partly from the description and partly from the practice of the invention. EXPLANATION OF THE FIGURES To complement the description being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of its practical embodiment, a set of drawings is included as an integral part of said description, in which the following has been represented for illustrative and non-limiting purposes. In Figure 1, we can observe the mask of the high melting point ink. In Figure 2, we can see first the mask or negative of the image to be printed, then a first set of prints in one color, followed by a second set of prints in a second color, illustrating the layering process. In the figure, "Mask" refers to the mask, "Black" to black, and "White" to white. Figure 3 shows the relative arrangement of the different prints made on the same side of a glass panel. In the figure, Mask refers to the mask, Black to black, and White to white. Figure 4 shows the appearance of the glass after the second color has been printed over the mask made with a high-melting-point ink. In the figure, "Mask" refers to the mask. Figure 5 shows the appearance of the glass surface after the high-melting-point ink is removed by washing with water, leaving only the ink of the different colors. In the figure, "Mask" refers to the mask. Figure 6 illustrates how two people, each looking through one side of the glass, perceive different colors. In the figure, Black sees black and White sees white. PREFERRED EMBODIMENT OF THE INVENTION In view of the figures, a preferred embodiment of the proposed invention is described below. In Figure 1 we can observe a mask (1) which is the negative of the surface to be printed and where this mask (1) is made with an ink with a high melting point >800ºC, and has a series of holes (5) which is where a first ink or a first layer of a series of surfaces will be deposited, for example, black dots (2), of a size slightly larger than the size of the holes (5) and a second ink or second layer of, for example, white dots (3) of size and arrangement coinciding with the projections of the black dots (2). Figure 3 shows how a mask (1) is placed on a glass surface (4), which is the negative of the image to be made and which is provided with a series of holes (5), on which a first group of surfaces of a first color is projected, for example, black dots (2) and on these a second group of surfaces of a second color is projected, for example, white dots (3). Figure 4 shows how, when magnifying the surface of the glass, it can be seen that the holes (5) of the mask (1) are covered by a double layer of printing inks of different colors, where only the last color applied would be observed, in this case, white dots (3), showing the imprecision (6) of the printing that is superimposed on the mask (1). Thanks to the fact that the ink used in printing the mask (1) is an ink with a high melting point, the inaccuracies (6) generated in the printing of the positive, that is, the white dots (2) and black dots (3) that are superimposed on the high melting point ink of the mask (1) can be easily removed by a process, for example, washing. Figure 5 shows the process of removing the mask (1) by means of a water spray, which would remove all the ink that protrudes from the perimeter edges of the openings (5), that is, the inaccuracies (6) (Figure 4). Since the surfaces of the first and second colors are coincident, the glass viewed from one side presents one color, while the same glass viewed from the other side presents a different color. This is the effect produced by two observers viewing the same glass from different sides, each seeing a different color, as shown in Figure 6. The procedure that is the subject of the invention comprises the following steps: - printing a negative design to the desired final design with a high melting point ink >800°C forming a mask (1) that has a series of gaps (5), - printing of first surfaces on the holes (5) of the mask (1) larger than the holes (5) and with a first ink that has a first color, - printing of second surfaces over the first surfaces that have been printed over the holes (5) and which are also larger than the holes (5) being done with a second ink that has a second color, - final drying, - vitrified, where after vitrification the two inks, of the first ink and of the second ink, which, for example, can be white ink and black ink printed superimposed in the gap left by the high melting point ink will be fused onto the glass (4), - Removal of all printed inks on the mask (1) that have fallen onto the high melting point ink, either due to excess size or mechanical and firing tolerances, after a washing process with pressurized water or any other washing method Optionally, after printing with the high melting point ink, an intermediate drying process is carried out. Additionally, after the first surfaces are printed with the first ink, an intermediate drying process takes place. For the composition of the mask ink we will use materials or oxides with a high melting point, for example, melting point >800ºC, such as silica, zirconium oxide, magnesium oxide, beryllium oxide, aluminum oxide, and the corresponding additives and solvents to obtain a digital printing ink. Ink example 1: - Silica with a D90 particle size of less than 2 microns 35-45%, - Zirconium Oxide with a D90 particle size of less than 2 microns 5-15%, - Solvent DPM (methoxy propanol) 35-45%, - Dispersant additive type BYK 1803-6%, - Methoxycellulose 2-5%. Ink example 2: - Beryllium oxide at a D90 particle size of less than 2 microns 35-45%, - Aluminum oxide with a D90 particle size of less than 2 microns 5-15%, - Solvent DPM (methoxy propanol) 35-45%, - Dispersant additive type BYK 1803-6%, - Methoxycellulose 2-5%. Ink example 3: - Oxide or material with a melting point >800 degrees and a D90 particle size less than 2 microns 35-45%, - Aluminum oxide with a D90 particle size of less than 2 microns 5-15%, - Solvent DPM (methoxy propanol) 35-45%, - Dispersant additive type BYK 1803-6%, - Methoxycellulose 2-5%. The solvent can be changed to a non-polar hydrocarbon solvent, and in this case the dispersant would also be changed to a commercially available one compatible with hydrocarbons; similarly, the methoxycellulose would be changed to a hydrocarbon-compatible resin. Having sufficiently described the nature of the present invention, as well as the manner of putting it into practice, it is stated that, within its essential nature, it may be put into practice in other forms of embodiment that differ in detail from the one indicated as an example, and which will also achieve the protection sought, provided that it does not alter, change or modify its fundamental principle.

Claims

1. A method for printing on glass for double vision, characterized in that it comprises the following steps: - printing a negative of the desired design with a high melting point ink (>800°C) forming a mask (1) that has a series of recesses (5), - printing first surfaces onto the recesses (5) of the mask (1) that are larger than the recesses (5) with a first ink having a first color, - printing second surfaces onto the first surfaces that have been printed onto the recesses (5) and that are also larger than the recesses (5) with a second ink having a second color, - final drying, - vitrification of the first and second printed inks superimposed in the recess left by the high melting point ink, which will be fused onto the glass (4), - removal of all the inks printed on the mask (1) that have fallen onto the high melting point ink,either due to excess size or mechanical and firing tolerances, after a washing process with pressurized water or any other washing method.

2. A method of printing on glass for double vision according to claim 1, characterized in that an intermediate drying process is carried out after printing with the high-melting-point ink.

3. A method of printing on glass for double vision according to claim 1, characterized in that an intermediate drying process takes place after printing the first surfaces with the first ink.

4. A high-melting-point ink for carrying out the method described above according to any of the preceding claims, characterized in that the composition of the high-melting-point ink comprises high-melting-point oxides such as silica, zirconium oxide, magnesium oxide, beryllium oxide, aluminum oxide, or any other oxide or material with a high melting point >800 degrees.Additives and solvents to obtain a digital printing ink.

5. High melting point ink according to claim 4 characterized in that the ink comprises: - Silica with a D90 particle size of less than 2 microns 35-45%, - Zirconium Oxide with a D90 particle size of less than 2 microns 5-15%, - DPM solvent (methoxy propanol) 35-45%, - BYK 1803-6% dispersing additive, - Methoxycellulose 2-5%.

6. High melting point ink according to claim 4, characterized in that the ink comprises: - Beryllium oxide with a D90 particle size of less than 2 microns, 35-45%; - Aluminum oxide with a D90 particle size of less than 2 microns, 5-15%; - DPM (methoxypropanol) solvent, 35-45%; - BYK 1803-6% dispersing additive; - Methoxycellulose, 2-5%.

7. High melting point ink according to claim 4, characterized in that the ink comprises: - Oxide or material with a melting point >800 degrees, with a D90 particle size of less than 2 microns, 35-45%.- Aluminum oxide with a D90 particle size of less than 2 microns 5-15%, - DPM solvent (methoxypropanol) 35-45%, - BYK 1803-6% dispersing additive, - Methoxycellulose 2-5%.

8. High melting point ink according to any of claims 5 to 7, characterized in that the solvent is a non-polar hydrocarbon solvent.

9. High melting point ink described according to any of claims 5 to 7, characterized in that the dispersant is a hydrocarbon-compatible dispersant.

10. High melting point ink described according to any of claims 5 to 7, characterized in that the methoxycellulose is likewise replaced by a hydrocarbon-compatible resin.

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