DE102022111945A1 - Glass pane comprising at least one coating applied in at least one area of at least one side of the glass pane, paste for producing such a glass pane and composite comprising such a pane and its use - Google Patents

Abstract

The present invention relates generally to glass panes, in particular to those glass panes which have a coating in at least one region of at least one side of the glass pane. In particular, the invention relates to glass panes comprising a glass comprising SiO2 and B2O3, as to glass panes made of or comprising a borosilicate glass. The invention further relates, according to a further aspect, to a paste for producing such a glass pane, to a composite which comprises such a glass pane, and its use.

Description

Field of invention

The present invention relates generally to glass panes, in particular to those glass panes which have a coating in at least one region of at least one side of the glass pane. In particular, the invention relates to glass panes comprising a glass comprising SiO ₂ and B ₂ O ₃ , and in particular to glass panes made of or comprising a borosilicate glass. The invention further relates, according to a further aspect, to a paste for producing a coating of such a glass pane, to a composite which comprises such a glass pane, and the use thereof.

Background of the invention

Glass panes made of or comprising borosilicate glasses, in particular those that are at least partially coated, have been known for a long time and are used, for example, as oven viewing panes in oven doors. The advantages of borosilicate glass here are its thermal resistance compared to conventional soda-lime glasses, so that, for example, oven viewing panes for pyrolysis ovens often include such borosilicate glass panes.

But borosilicate glasses can also be advantageous for other applications, since such glasses have inherent advantages, for example in terms of scratch resistance or general mechanical resistance as well as chemical resistance compared to the known soda-lime glasses. This is why such borosilicate glass panes are increasingly being used in windshields.

It is known to use borosilicate glass, for example, such as is commercially available under the trade name Borofloat®, in the exterior glazing of vehicles. Such glass is, for example, very suitable for laminate glazing and is characterized by a very high transmission in the visible light range. Furthermore, such borosilicate glasses have very good heat resistance, high chemical resistance and good mechanical strength.

For example, the international patent application describes WO 2015/059406 A laminated glass panels. One of these panes can, for example, comprise a borosilicate glass, for example the outer pane.

The international patent application WO 2017/157660 A1 describes a laminated glass pane for a head-up display. Here too, one of the panes of the laminated glass can comprise borosilicate glass.

CO 2017/0005596 A1 also describes a car glass pane with high durability.

The international patent application WO 2019/130285 A1 describes a laminate with high resistance to abrasion and environmental influences.

Finally describes the international patent application WO 2018/122769 A1 a laminate with high breaking strength.

For the safety of vehicle occupants, windshields are designed as laminated glass panes and usually have a coating in the edge area. On the one hand, this coating serves to optically conceal, for example, bonds or components such as antennas, and on the other hand it also protects them from UV radiation. As a rule, this frame is arranged between the two glass panes of a composite. The composite further comprises a polymeric layer, thus a layer comprising a polymer or consisting of a polymer, between the two glass panes, which connects the glass panes to one another. The glass panes with the coating arranged between them in at least one area, in particular in the edge area, are placed on top of each other and bent in a thermal forming process. A polymeric layer is then placed between both panes and the curved glass panes are connected to one another, so that a laminated glass pane (which is also simply referred to as a “laminate” in the context of the present disclosure) is ultimately obtained.

A number of requirements are therefore placed on glass panes that are included in such a composite. Since the bending processes are thermal, the glass panes and the coating applied to them must be able to withstand these temperatures. The glass panes and the coating must be able to form a bond with the polymeric layer in such a way that a stable bond is formed and there is no delamination between the glass and the polymer. Finally, it is necessary that the coating has sufficient optical tightness so that components that are arranged in the frame area of the windshield are not disturbingly visible. This prevents the driver from being distracted and thus increases driving safety. Microcracks or other defects in the coating should also be avoided or at least minimized if possible.

In addition to the temperature resistance of glass and coating, the mentioned compatibility of glass or coating with a polymeric material to form a composite, the optical density and the minimization of possible defects, the mechanical strength, for example characterized by the breaking strength, of a coated glass pane also plays a role Role. It is known that coatings, especially particularly adhesive coatings, can impair the strength of a glass pane. Particularly adhesive coatings such as glass-based coatings can critically reduce mechanical strength, such as breaking strength or bending strength. In principle, this applies to all glass substrates, but even more so when the substrate, in this case the glass pane, has a low coefficient of expansion, as is the case with borosilicate glass panes. For example, when using known ceramic colors, differences in the expansion coefficients of the coating and substrate can occur, which are considered to be the cause of the observed loss of strength in coated glass panes.

There is therefore a need for coated glass panes that at least mitigate the aforementioned weaknesses of the prior art.

Task of the invention

The object of the present invention is to provide a glass pane for a vehicle that is coated at least in some areas and which at least partially reduces the aforementioned weaknesses of the prior art. Further aspects of the invention are directed to a paste, in particular for producing a coating of such a glass pane, a composite which comprises such a glass pane, and their use.

Summary of the invention

The object of the invention is solved by the subject matter of the independent claims. Preferred and specific embodiments can be found in the dependent claims, description and drawings of the present disclosure.

The invention therefore relates to a glass pane for a vehicle comprising a glass comprising SiO ₂ and B ₂ O ₃ The glass pane has at least one coating with a first coating applied to at least one region of at least one side of the glass pane. The first coating comprises at least one binder comprising SiO ₂ , at least one pigment and at least one additive. The glass pane has a bending strength between at least 5 and at most 170 MPa, preferably at least 20 and at most 170 MPa, particularly preferably at least 35 MPa, very particularly preferred, in the at least one area which has the applied first coating on the at least one side of the glass pane at least 60 MPa, and most preferably at least 80 MPa. The binder is glass-based and is designed as a glass frit and the coating is designed as an enamel layer. The additive is a filler.

A glass pane for a vehicle is generally understood to mean a glass pane for mobile applications, for example for aircraft and/or automobiles.

Such a glass pane has a number of advantages.

In the present case, the glass pane comprises a glass comprising SiO ₂ and B ₂ O ₃ , i.e. a so-called borosilicate glass. This type of glass material (or glass for short) is a chemically very resistant material that is also mechanically resistant and, compared to conventional glasses such as soda lime glasses, has good thermal resistance and good mechanical strength in one has a prestressed state. It has also been shown that the scratch resistance of such borosilicate glasses is higher than that of soda lime glasses.

The coating is formed in at least one area on at least one side of the glass pane. The coating is preferably designed in the form of a frame over the entire edge region of one side of the glass pane, although it is also possible for the coating to no longer be opaque towards the central region of the glass pane, but rather to be applied in the form of a so-called dot grid. This can be advantageous if the glass pane is used as part of a composite that is used as a windshield.

It can be advantageous here, for example, if the coating has an optical density for the thicknesses of the coating specified in more detail below, which is at least 1 and at most 4.5, preferably more than 2. The optical density is determined in an area in which the coating is applied over the entire surface.

In the present case, the coating is designed as a chemically and thermally resistant coating. This means that the coating comprises a binder comprising SiO ₂ . SiO ₂ has good chemical resistance and is also temperature stable.

The coating further comprises at least one pigment. In the context of the present disclosure, a pigment is understood to mean a particle-based color body. The pigment according to the present disclosure is also advantageously designed to be temperature-stable, and it is preferably a ceramic colored body. In the context of the present disclosure, a color body (or pigment) is generally understood to mean that the color body consists of particles, which can also be referred to here as pigment particles. If it is stated in the context of the present disclosure that a coating comprises a pigment, this is understood to mean that the coating comprises particles of a specific pigment or color body, i.e. particles with the composition of the pigment or color body.

Ceramic colored bodies or ceramic pigments as such are known to those skilled in the art. For example, these can be metallic mixed oxides such as spinels, hematites or pure oxides such as TiO ₂ .

Furthermore, the first coating comprises an additive, namely a filler. According to one embodiment, the first coating can additionally comprise a further additive. However, this is not generally necessary, and it may also be preferred that the first coating only comprises a single additive, namely a filler, and no further additive.

The inventors have discovered that particularly good strength of the coated glass pane can be achieved in this way. They suspect that this is because a particularly good layer structure can be achieved in this way, in which a certain porosity can be achieved in the coating through a uniform distribution of fillers in the coating. In particular, as will also be shown in the figures, with such a design of glass panes there appears to be a porosity in the coating, which is directed in particular towards the coating/glass pane interface, i.e. in the area of the so-called melting reaction zone.

According to one embodiment, the glass pane is therefore designed such that it has a porosity gradient, with the porosity of the coating decreasing from the glass pane towards the surface of the coating.

If reference is made to a glass pane in the context of the present application, this is a coated glass pane, unless expressly stated otherwise.

The coated glass pane according to embodiments generally has, in particular in the area in which the presently disclosed coating is applied, a flexural strength between at least 5 and at most 170 MPa, preferably at least 20 and at most 170 MPa, particularly preferably at least 35 MPa, very particularly preferably at least 60 MPa , and most preferably at least 80 MPa. In this way, the coated glass pane has sufficient strength for use, for example, as a pane in a composite. The bending strength of the (coated) glass pane is preferably at least 50% of the bending strength in the coated area uncoated glass pane. The bending strength of an uncoated glass pane of the same composition and design is preferably between at least 100 MPa and at most 210 MPa, for example around 150 MPa. The mechanical strength, such as the bending strength, is a statistical value, so of course the same pane would not be examined for bending strength before and after coating; Rather, this statement above refers to studies that were carried out on uncoated glass panes and coated glass panes of the same composition and design. In the context of the present disclosure, bending strength is understood to mean a strength of the glass pane, also known as double ring bending tensile strength, which was determined in accordance with DIN 1288-5. In the context of the present disclosure, the arithmetic mean is given as the strength value.

According to one embodiment, the level of surface coverage of the at least one side of the glass pane with the coating is at least 10% and at most 80%, preferably at least 15% and at most 65% of the total surface of the side of the pane to which the coating is applied.

In the context of the present disclosure, a disk is generally understood to mean a plate-shaped molded body. A glass pane (which can be coated and uncoated) is a pane comprising or made of glass. A shaped body is plate-shaped if its spatial dimensions in one spatial direction of a Cartesian coordinate system are at least one order of magnitude smaller than the spatial dimensions in the two other spatial directions of the Cartesian coordinate system that are perpendicular to the first spatial direction. In other words, the thickness of the shaped body is at least an order of magnitude smaller than its length and width. The two main surfaces or main surfaces of the pane, i.e. those whose size is determined by length and width, are also referred to simply as sides in the context of the present disclosure.

According to a further embodiment, the visual transmittance, τ _vis , in the at least one area of the glass pane in which the coating is arranged is at most 10%, preferably at most 7% and particularly preferably at most 5%, very particularly preferably at most 1%. According to one embodiment, τ _vis is at least 0.05% and preferably at most 0.3%. These values refer to an area in which the coating covers the entire surface of the glass pane.

The coating can be applied to the glass pane in at least one area in a covering manner, i.e. "over the entire surface" relative to the area, i.e. without interruption in the coating, but can also be arranged, for example, in the form of a so-called dot grid. Combinations of these variants are also possible. For example, it is also possible for a coating arranged on the glass pane over the entire surface, i.e. without interruptions in the coating, to merge into a dot grid in the edge region of the coating, usually towards the center of the glass pane. This is, for example, a common design of the coating, which in this case is arranged in a structured manner on the glass pane, for glass panes that are used in vehicle windshields.

The binder is generally glass-based, more specifically as a glass frit. The coating is generally designed as an enamel layer.

According to the presently preferred embodiments, the coating has a thickness between 3 μm and 30 μm, preferably between 4 μm and 15 μm, particularly preferably less than or equal to 13 μm.

According to one embodiment, the filler comprised by the first coating is a filler with a linear thermal expansion coefficient between -10 * 10 ^-6 /K and +10 * 10 ^-6 /K. The linear thermal expansion coefficient is preferably between -8 * 10 ^-6 /K and +5 * 10 ^-6 /K, particularly preferably between -6.5 * 10 ^-6 /K and +3 * 10 ^-6 /K.

According to yet another embodiment, the glass pane has an optical density of at least 1 and at most 4.5 for the coating thicknesses specified above in the at least one area in which the coating is arranged. Optical density or color density is used to characterize the absorption behavior of a coating compared to an “absolute white”. The denser the layer of paint, the less light can pass through it. The optical density is calculated using the following formula: $$D=\text{log}\left(\frac{1}{R}\right)$$

R is the degree of remission. The optical density is determined using densitometers, particularly in the context of the present disclosure in the perpendicular direction to the largest surface extent of the coating and thus the coated surface of the coated glass pane. The higher the optical density, the less transparent the coating appears.

A glass-based coating is generally understood to mean a coating which has an at least predominantly, i.e. more than 50% by weight, inorganic, amorphous binder. In particular, such a glass-based coating can also have a binder which is essentially, i.e. at least 95% by weight, or even completely inorganic and amorphous. In addition to the binder, a glass-based coating can generally include other components. The glass-based coating according to the present disclosure is further formed here as an enamel layer. According to the present disclosure, the coating here also comprises at least one pigment and at least one additive, which is designed as a filler.

A glass-based coating can generally also be understood as meaning a coating which comprises a sol-gel-based binder.

However, according to the present disclosure, the glass-based coating is designed as an enamel coating.

In the context of the present disclosure, enamel coatings or enamel layers are understood to mean coatings which have a glass frit or glass flow as a binder. When such coatings are baked, the components of the glass flow, thus the glass frit, melt and a melting reaction zone can form on the surface of the substrate, for example the glass pane. In the context of the present disclosure, the terms frit, glass frit or glass flow are used synonymously for each other. Furthermore, the molten glass flows and envelops any additional components that may be included in the enamel paint or the coatings resulting from such a paint, such as pigment particles and/or filler particles. Enamel layers are therefore particularly advantageous. In this way, particularly mechanically resistant coatings can be obtained. In addition, the surface of such a layer is glass-like and may even be quite similar to the composition of the glass of the glass pane, depending on the exact composition of the glass frit. In this way, it is advantageously possible for the strength of the connection between the two glass panes of a composite not to differ greatly in different areas, but for the connection to be uniform over the entire side of the glass pane.

In the context of the present disclosure, a glass flow or (synonymously) a glass frit is understood to mean a glass-based binder which is suitable for forming a glaze and/or enamel layer. In particular, this can be a glass powder which is suitable and intended to be applied to a substrate by means of a printing process, whereby the glass powder can also be mixed with other components, for example pigments. Such glass flows/glass frits preferably have a lower melting point and/or softening point than the corresponding substrate material, in particular than the material of a glass pane to be coated.

According to a further embodiment, a further coating, in particular as an intermediate layer between the glass pane and the first coating, is arranged in at least a portion of the area of the at least one side of the glass pane in which the first coating is applied. In this further embodiment, the entire coating disclosed herein thus comprises the first coating and the further coating. For the sake of linguistic brevity, the entire coating is sometimes simply mentioned below as a coating.

Such a further coating, which is arranged as an intermediate layer between the glass pane and the coating, can be very advantageous, especially for those designs of the glass pane in which the difference in the linear thermal expansion coefficients between the coating and the glass pane is so large that it becomes critical A decrease in the strength of the coated glass pane occurs. In this case, the further, between the first, pigmented coating and the coating arranged on the glass pane act as a kind of compensating layer. A similar type of coating is described as an example in the European patent EP 3 022 164 B1 .

Such a further coating or intermediate layer is particularly advantageous if, as according to the present disclosure, the first, pigmented coating is designed as an enamel layer. As described above, with such enamel coatings, a so-called melting reaction zone often forms at the contact between the surface of the substrate, i.e. here the glass pane, and the coating due to the melting of the glass flow/glass frit. On the one hand, this intimate connection leads to great adhesive strength of the coating, but it can also lead to cracks forming in the event of large differences in the linear thermal expansion coefficients. In contrast to glass-based coatings, which do not include enamel but, for example, a sol-gel binder, an enamel coating, which is also referred to as a frit coating in the context of the present disclosure, forms a reaction zone. When coating a glass substrate, such as a glass pane, this reaction zone is very fine and cannot be seen or can only be seen with difficulty in the SEM. Cracks do not necessarily form, but it may be that the reaction zone has different mechanical properties than the glass pane and the first coating. If only one such reaction zone is formed, its specific formation with different properties than the substrate (here the glass pane) and the first coating can lead to a reduction in the strength of the coated pane. If cracks form, they are not only disturbingly visible, but can also seriously affect the strength of the coated substrate, in this case the glass pane. In particular, it may be possible that, depending on the exact design of the coating and/or the glass pane, there is insufficient flexural strength of the coated glass panes between at least 5 and at most 170 MPa, preferably at least 20 and at most 170 MPa, particularly preferably at least 35 MPa, very particularly preferably at least 60 MPa, and most preferably at least 80 MPa more. Here, an intermediate layer can serve as a further coating, for example a glass-based layer, in particular a glass flow-based layer, as a type of adaptation layer. In particular, such a further coating can be unpigmented. It can be advantageous if the further coating or intermediate layer comprises the same glass flow as the first pigmented coating, but is pigment-free. In this case, a gradient-like transition can result between the further coating and the first coating. Another type of intermediate layer consists of a porous layer with, for example, a high pigment content, which absorbs the stresses, and an overlying sealing layer made of frit with little to no pigment.

The terms “further coating” and “first coating” do not refer to the order of application, but simply to the fact that the “first coating” is always present, but the further coating can only be present optionally, i.e. according to embodiments.

However, in general, without limitation to the above-described embodiment of the further coating as an adaptation layer, it is also possible for the further coating to perform other functions and/or have a different glass flow or a different glass frit than the first coating and/or as non-glass-based Coating or at least not designed as an enamel layer.

Thus, depending on the embodiment, the coating disclosed herein may comprise the first coating and the further coating as an intermediate layer or may only comprise the first coating.

In general, the paste for the first coating comprises between 0.5% by volume and 50% by volume of pigment, preferably less than 40% by volume of pigment, and between 50% by volume and 99.5% by volume of glass frit, based on the solids content contained in the paste.

According to a further embodiment, the first coating comprises between 0.5% by volume and 50% by volume of pigment, preferably between 0.5 and 40% by volume of pigment, particularly preferably between 20 and 40% by volume of pigment.

The binder content in the first coating is between 99.5% by volume and 40% by volume of binder, preferably between 99.5 and 50% by volume of binder, particularly preferably between 80 and 55% by volume of binder, for example between 80 and 60% by volume of binder, namely glass-based binder, with a glass frit forming the binder.

A design of the coating and, in a corresponding manner, the glass pane provided with the coating can be advantageous because in this way a coating can be obtained which is sufficiently optically dense. Because of the pigment content, in particular of at least 0.5% by volume of pigment, in particular in the first coating, the thicknesses of the entire coating disclosed here ensure that an optically dense, preferably even opaque coating is obtained. This can therefore be used accordingly, for example to conceal components or elements arranged in the frame area of a windshield. Preferably, the pigment content can also be higher and, for example, be 10% by volume or even more.

However, the pigment content should generally not be too high. The pigment content of the coating in the first coating is preferably not greater than 50% by volume and is preferably at most 40% by volume, particularly in the case that an uncolored glass frit is used as a binder. In this way it is ensured that a sufficient proportion of binder is present. As stated, the binder preferably envelops the pigment particles and in this way connects them to one another and to the substrate - in this case the glass pane - to form a well-adhering coating, in particular even if the intermediate layer described here is arranged between the coating and the glass pane.

If the coating, in particular the first coating, only comprises the binder in addition to the pigment or pigment particles, the volume proportions of binder and pigment preferably add up to 100. In other words, the coating according to this embodiment comprises between 99.5% by volume and 50% by volume of binder, i.e. glass flow/glass frit. Furthermore, the proportion of at least one additive designed as a filler also counts. The volume determines the mechanical and optical properties. When calculating the composition of the coating, in particular the first coating, the solid composition was assumed. In the event that the coating comprises another additive in addition to at least one pigment, the additive designed as a filler and the glass flow, a distinction must be made: If this additive is a blowing agent, this additive is not included in the solids content, but rather charged additionally. This means that in the case of a coating with pores, the final layer composition is inorganically the same as a dense layer, but there are additional pores built in. If the additional additive is a filler, i.e. a solid substance that does not decompose and the coating is installed, this is taken into account in the usual way when calculating the solids content.

Advantageously, the above-mentioned volume ratio between pigment and binder is also maintained according to one embodiment if the coating also comprises further components, for example a certain proportion of further additives, such as fillers or pore formers.

According to yet another embodiment, the glass of the glass panes has a linear thermal expansion coefficient between 2 * 10 ^-6 /K and 6 * 10 ^-6 /K. This is advantageous because in this way it is possible to design the glass pane using known, low-expansion borosilicate glasses, which already have a very high intrinsic glass strength. Furthermore, such glasses also have quite good thermal stability and are also quite chemically resistant.

According to one embodiment, the glass of the glass pane advantageously comprises at least 60% by weight of SiO ₂ to at most 85% by weight of SiO ₂ and/or at least 7% by weight of B ₂ O ₃ to at most 26% by weight of B ₂ O ₃ . Such glasses are particularly advantageous because they offer a good compromise between good mechanical, chemical and thermal resistance on the one hand and good meltability on the other hand, without segregation tendencies and/or excessive viscosity of the glass melt having a disruptive effect.

According to one embodiment, the first coating advantageously has a linear thermal expansion coefficient between at least 3 * 10 ^-6 /K and at most 10 * 10 ^-6 /K, preferably less than 9 * 10 ^-6 /K, particularly preferably less than 7 .5 * 10 ^-6 /K, most preferably less than 6 * 10 ^-6 /K. This embodiment can advantageously be linked to or attached to versions of the glass pane in which the linear thermal expansion coefficient of the glass of the glass pane is also limited and lies between 2 * 10 ^-6 /K and 6 * 10 ^-6 /K. In this way, glass panes comprising a pigmented coating with a glass-based binder which have sufficient flexural strength can be obtained in a particularly simple manner. However, it is generally also possible to use coatings with linear thermal properties to combine expansion coefficients within the aforementioned limits with glass panes which have a significantly higher, different linear thermal expansion coefficient and vice versa. However, other measures will then be taken to compensate for the difference in expansion coefficients. For example, as already described above, this can be done using a so-called adaptation layer or intermediate layer as a further coating.

However, other options are also conceivable in principle.

For example, it is generally conceivable to design, in particular, the first coating in such a way that, in addition to the glass-based binder, the filler and the pigment, it also includes one or, if appropriate, several further additives.

In the context of the present disclosure, an additive is generally understood to mean a solid which is added to a coating composition, preferably in particulate form or as a powder.

Such an additive can be, for example, a filler. In the context of the present disclosure, a filler is understood to mean, in particular, inorganic solids which do not act as color bodies in a coating. These are solids that do not act as a pigment themselves, but are added to the coating for other reasons. For example, such fillers can be used to improve scratch resistance, or to deflect cracks (platelet or needle-shaped), or to set a lower expansion coefficient α of the composite layer, in particular the first coating.

In general, a design of the coating in such a way that it comprises at least one additive in the form of a filler is very advantageous, especially in the case of large differences in the thermal expansion coefficient of the glass pane (or the glassy material of the glass pane) and the coating. It is therefore provided that the first coating comprises at least one filler.

It can be particularly advantageous if the filler is designed in such a way that it can at least reduce thermal expansion coefficient differences between the pigment or pigments used, the glass flow/binder and the substrate. Therefore, according to one embodiment, it is provided that the filler is a filler with a linear thermal expansion coefficient between -10 * 10 ^-6 /K and +10 * 10 ^-6 /K. The linear thermal expansion coefficient is preferably between -8 * 10 ^-6 /K and +5 * 10 ^-6 /K, particularly preferably between -6.5 * 10 ^-6 /K and +3 * 10 ^-6 /K.

If reference is made to the thermal expansion coefficient in the context of the present application, this is understood to mean the linear thermal expansion coefficient α. Unless stated otherwise, this is specified in the range of 20-300°C. The terms α and α _20-300 are used synonymously in the context of this invention. This can be determined in particular for glassy materials using a method according to ISO 7991. The thermal expansion coefficient of the coating is understood to mean the resulting thermal expansion coefficient of the corresponding coating, which is derived from the thermal expansion coefficients of the individual components of the coating, taking into account their share in the Coating results. If, in the context of the present application, the focus is on the thermal expansion coefficient of the glass pane, what is always meant is the thermal expansion coefficient of the glassy material (or glass) of the glass pane (i.e. the substrate).

As stated above, an additive, in particular in the form of a low-expansion filler, is a possibility of specifically adjusting, in particular minimizing, the coefficient of thermal expansion and, in a corresponding manner, the difference in coefficient of expansion between the coating and the glass pane. For example, such a filler can be a low- or even negative-elongation filler, for example silica or β-eucryptite or cordierite. Alternatively or additionally, the filler can also, as stated above, be used to improve scratch resistance or to deflect cracks (platelet or needle-shaped). In particular, a crack deflection can, for example, help to at least partially minimize or mitigate the consequences of the resulting crack energy, so that the overall mechanical properties of the glass pane are essentially preserved together with the first coating with the additive or also together with the first coating with the additive and the intermediate layer remain, or at least not be discounted too much.

Alternatively or additionally, another embodiment of an additive is also possible. For example, so-called foaming agents can be used. These are agents which decompose under the influence of heat when the coating is burned in, forming a fluid phase, preferably a gas phase. This can cause bubbles to form in the coating. Such bubbles or pores in a coating can also reduce the thermal expansion coefficient of the coating. Known foaming agents are, for example, generally carbonates or phosphates, but also organic additives such as starch or sugar.

According to a preferred embodiment, it can therefore be provided that the coating comprises a further additive in addition to the at least one additive designed as a filler. This further additive can be a filler or a foaming agent (also referred to as a blowing agent). In particular, it is also possible for the coating to comprise several further additives, for example a filler and a foaming agent, or even several further fillers and/or several foaming agents.

According to yet another embodiment, the glass pane has a thickness between at least 1 mm and at most 12 mm.

According to yet another embodiment, the binder comprises or consists of a glass frit, wherein the glass frit comprises a coloring component, and/or wherein the proportion of the pigment in the respective first coating is at most 40% by volume, preferably at most 20% by volume. , includes. It can preferably be provided that the glass frit comprising a coloring component is combined with a pigment content of at most 40% by volume, preferably 20% by volume.

Such a design of the coating and, in a corresponding manner, of the glass pane can be advantageous if the pigment content of the coating is to be kept low. This may be desired for several reasons. Pigments are usually relatively high-priced components, especially those that have a high color strength. It can therefore be economical if a coating has the lowest possible proportion of pigments.

Furthermore, ceramic pigments commonly used in a coating can have a relatively high coefficient of thermal expansion compared to borosilicate glasses, for example spinel-based pigments. Therefore, from the perspective of ensuring that the thermal expansion coefficient of the respective coating is as low as possible, it may be advantageous to limit the pigment content of the coating.

However, this can be bad from the point of view of the hiding power of the resulting coating. If the pigment content is too low, it may be that a coating that does not have sufficient coverage is obtained or that the coating would have to have a very high layer thickness in order to be opaque. Layer thicknesses that are too high are not only unfavorable for cost reasons (due to the high amount of material used), but can also lead to spalling and cracking.

It can therefore be advantageous to select the binder, in particular a glass frit, in such a way that it contains a coloring component if the pigment content in the coating, in particular the first coating, is only low. In this way, the glass frit also contributes to the opacity of the coating. Furthermore, it may also be the case that disturbing colorings caused by the pigment (for example an undesirable brown tint, which occurs more often with black pigments) can be actively countercolored by the glass frit, thus obtaining a particularly neutral, dark, black color impression. This is an advantage for driver safety, especially with coatings used on glass composites in the vehicle sector. In this way, the driver is not disturbingly distracted by a uniform color impression in the edge area of a window.
According to a further aspect, the disclosure also relates to a paste. This is a paste for producing a coating on a glass pane, preferably a first coating of a glass pane, as described according to embodiments of the present disclosure.

• - wenigstens ein Bindemittel umfassend SiO₂,
• - wenigstens ein Pigment und
• - wenigstens einen als Füllstoff ausgebildeten Zusatzstoff,
• - vorzugsweise wenigstens ein Dispersionsmedium.

The paste includes

• - at least one binder comprising SiO ₂ ,
• - at least one pigment and
• - at least one additive designed as a filler,
• - preferably at least one dispersion medium.

The medium or dispersion medium is advantageous for applying the paste to the glass pane, for example for applying the paste using a screen printing process.

The binder comprises or consists of a glass frit, the glass frit comprising a glass comprising at least the following components in% by weight on an oxide basis: _SiO2 10 to 70 _{B2O3 _} 10 to 26 _{Al2O3 _} more than 0 to 9.

In the case of frits with a high Bi content, in particular borosilicate frits with a high Bi content, the glass frit can comprise a glass which comprises at least the following components in % by weight on an oxide basis: Areas of high Bi-containing borosilicate frits _{Bi2O3 _} 8-45 _{B2O3 _} 15-25 _SiO2 30-60 Sum R ₂ O 4-5 alkali oxides Total RO <_0.5 Alkaline earth oxides

The frits specified in the previous paragraph can optionally have a proportion of Al ₂ O ₃ of more than 0 to 9% by weight.

The following applies to the thermal expansion coefficient α and the optical density for the above high Bi-containing borosilicate frits: α [* 10 ^-6 /K] Density [g/cm ³ ] min Max min Max 4.7 7.9 2.4 4

In the case of frits with a high Zn content, in particular borosilicate frits with a high Zn content, the glass frit can comprise a glass which comprises at least the following components in % by weight on an oxide basis: Areas of high Zn-containing borosilicate frits ZnO > 50 _{B2O3 _} 10-26 _SiO2 10-50 Sum R ₂ O ≤ 0.5 alkali oxides Total RO ≤ 0.5 Alkaline earth oxides

The frits specified in the previous paragraph can optionally have a proportion of Al ₂ O ₃ of more than 0 to 9% by weight.

The following applies to the thermal expansion coefficient α and the optical density for the above high Zn-containing borosilicate frits: α [* 10 ^-6 /K] Density [g/cm ³ ] min Max min Max 3.5 5.5 3.2 4

In the case of borosilicate frits, the glass frit can comprise a glass which comprises at least the following components in % by weight on an oxide basis: “Borosilicate” frit areas _{Bi2O3 _} 0-15 ZnO 0-5 _{B2O3 _} 15-26 _SiO2 50-70 Sum R ₂ O 4-6.5 alkali oxides Total RO 0-2.5 Alkaline earth oxides

The frits specified in the previous paragraph can optionally have a proportion of Al ₂ O ₃ of more than 0 to 9% by weight.

The following applies to the thermal expansion coefficient α and the optical density for the above borosilicate frits: α [* 10 ^-6 /K] Density [g/cm ³ ] min Max min Max 4 5.2 2.2 2.6

The paste here is designed in such a way that an enamel coating can be obtained with it, the glass frit advantageously comprising a borosilicate glass.

In the context of the present disclosure, a paste is understood to mean in particular a so-called decorative or color paste. In general, the paste comprises, in particular for the first coating according to the present disclosure, a glass frit (or a glass flow), at least one pigment and, in addition, preferably at least one fluid phase, which is also referred to as a medium or dispersion medium in the context of the present disclosure.

Solvents with a vapor pressure of less than 10 bar, in particular less than 5 bar and especially less than 1 bar, are preferably used as a medium for screen-printable coating solutions. These can be, for example, combinations of water, n-butanol, diethylene glycol monoethyl ether, tripropylene glycol monomethyl ether, terpineol, n-butyl acetate. In order to be able to set the desired viscosity, appropriate organic and inorganic additives are used. Organic additives can be, for example, hydroxyethyl cellulose and/or hydroxypropyl cellulose and/or xanthan gum and/or polyvinyl alcohol and/or polyethylene alcohol and/or polyethylene glycol, block copolymers and/or triblock copolymers and/or tree resins and/or polyacrylates and/or polymethacrylates . In general, commercially available screen printing media based on glycol or terpineol, for example, but also others are suitable.

In general, the paste according to embodiments can therefore be used to obtain a glass pane with a coating, the coating being an enamel layer and comprising a binder, here designed as a glass frit (or glass flow), which comprises the following components in% by weight on an oxide basis: _SiO2 10 to 70 _{B2O3 _} 10 to 26 _{Al2O3 _} more than 0 to 9.

The glass flow or glass frit of a paste generally forms the binding agent in the coating resulting from the paste, at least in the “pure” enamel layers. In general, it is also possible for the coating to include, in addition to a glass frit, another glass-based binder that does not consist of or is not derived from a glass frit, for example a sol-gel based one Binder. In this case, the binder of the coating is formed as a mixture of the different binders.

A paste as described above, in particular comprising or consisting of a glass frit comprising a glass comprising at least the following components in% by weight based on oxide: _SiO2 10 to 70 _{B2O3 _} 10 to 26 _{Al2O3 _} more than 0 to 9. can be particularly advantageous because in this way a binder for the coating is obtained, which itself is designed as borosilicate glass. Such borosilicate glasses can not only be designed so that they have a relatively low melting point (here B ₂ O ₃ advantageously acts as a so-called flow, which lowers the melting temperature and at the same time ensures that the binder flows well and the solid particles, in particular the pigment particles and can well envelop filler particles contained in the coating or paste) but, as stated above, also have a fairly high chemical resistance. Furthermore, such glass frits or the binders resulting from them are also well compatible with a substrate which is made of borosilicate glass, i.e. in particular the glass panes described here.

The paste is preferably designed such that it has a viscosity, preferably determined using a plate viscometer, between 1500 and 8000 mPas, preferably between 2000 mPas and 6500 mPas and particularly preferably between 2500 mPas and 5000 mPas. In this way, the paste can be easily applied to substrates, in particular to glass panes, using standard application methods. The paste can advantageously be applied to the substrate, i.e. the glass pane, using a printing process, in particular using screen printing.

The paste is preferably designed so that the glass frit comprised by the paste has a linear thermal expansion coefficient between at least 2 * 10 ^-6 /K and at most 10 * 10 ^-6 /K, preferably between at least 3 * 10 ^-6 /K and at most 6 * 10 ^-6 /K. In this way, it is possible to obtain coatings which advantageously enable sufficient strength of the glass pane, particularly in the case of preferably opaque coatings. Thermal expansion coefficients in the range between at least 3 * 10 ^-6 /K and at most 6 * 10 ^-6 /K are advantageous here, because these fit particularly well with known borosilicate glasses in terms of thermal expansion coefficient.

According to a further embodiment, the paste comprises between 0.5% by volume and 50% by volume of pigment, preferably less than or equal to 40% by volume of pigment, particularly preferably between 20 and 40% by volume of pigment on the solids content of the paste.

The glass frit content in the paste is between 99.5% by volume and 50% by volume, preferably between 99.5 and 60% by volume, particularly preferably between 80 and 60% by volume, based on that of the paste comprehensive solids content.

In this way - especially for the thicknesses of the coating disclosed here - coatings can be obtained which have sufficient opacity (or opacity), while at the same time the coating has sufficient scratch and adhesive strength.

As stated, the first coating includes a filler in addition to the pigment and the binder. The volume fraction of the binder remains within the aforementioned limits. In other words, the binder content preferably remains between 99.5% by volume and 30% by volume of glass frit. The additive in the form of the filler does not serve to form a bond between the particles of the coating and their connection to the substrate, but is itself part of the particulate component of the coating. The coating or the paste can therefore preferably be designed such that it generally comprises 99.5% by volume and 50% by volume of glass frit, preferably between 99.5% by volume and 60% by volume of glass frit, whereby the volume proportions here are based on the solids content of the paste. In addition, in the paste there is a solid, which is formed by the binder and the at least one pigment or, if appropriate, the sum of the pigments and an additive or, if necessary, several additives Other components, such as a solvent and, if necessary, an additive. The proportion of additive designed as a filler is preferably at most 25% by volume and particularly preferably at least 0.1% by volume. Preferred upper limits for the filler can be 20% by volume or 15% by volume, with preferred lower limits being 1% by volume and 5% by volume. The volume fractions here are based on the solids content of the paste. If the paste and/or the coating comprises several additives designed as fillers, the total filler content is taken into account here. The proportion of pigment is between 0.5% by volume and 50% by volume of pigment, preferably less than or equal to 40% by volume of pigment, particularly preferably between 20 and 40% by volume of pigment, whereby the Volume fractions here are based on the solids content of the paste. If the paste contains several pigments, the sum of the pigment content is used here.

According to one embodiment, the paste can further be designed so that it comprises a further additive, wherein the further additive is designed to change, in particular to lower, the resulting linear thermal expansion coefficient of the coating in comparison to a composition of the coating without the further additive, wherein the further additive is preferably a blowing agent or a filler, with particularly preferably the further additive being a filler with a linear thermal expansion coefficient between -10 * 10 ^-6 /K and +10 * 10 ^-6 /K. The linear thermal expansion coefficient is preferably between -8 * 10 ^-6 /K and +5 * 10 ^-6 /K, particularly preferably between -6.5 * 10 ^-6 /K and +3 * 10 ^-6 /K.

This embodiment is particularly advantageous if the first additive included in the first coating in the form of a filler itself has a different coefficient of thermal expansion, for example because the filler serves to improve other properties of the coating, for example to improve scratch resistance.

According to a preferred embodiment, the paste is designed such that the glass frit comprises a coloring component. In other words, the glass frit here is designed in such a way that it does not comprise or consist of uncolored glass, but is colored, preferably volume-colored, i.e. colored by coloring ions, or colored by crystal phases that occur during frit production or when baking the color arise. Such a design is particularly advantageous for low pigment contents, as described in detail above.

It should be noted here that the paste and the respective coating are related to each other in that the respective coating is formed from the solid component of the paste. In other words, the respective coating comprises the binder, which is present in the paste as a glass frit, as well as the particulate components, in particular the at least one pigment and possibly several pigments and / or the at least one additive designed as a filler and optionally further additives such as fillers . The coating does not contain, or only contains traces of, any fluid components of the paste, such as solvents, because these are burned out during baking.

In general, it is pointed out that in the present case it is also possible to obtain the first coating using a paste which comprises not only a glass frit as a binder, but an additional binder, for example based on sol-gel. However, such a configuration is generally not preferred because such pastes tend to be more difficult to process than pastes which only contain a glass frit as a binder. In particular, the pot life of such sol-gel-based or sol-gel-comprising pastes is generally short, and the viscosity can be unfavorable for common large-scale application processes, such as screen printing.

A further aspect of the present disclosure relates to a composite comprising an at least partially coated glass pane according to an embodiment of the disclosure and a further glass pane, the coating preferably being arranged between the glass panes. Furthermore, the composite preferably comprises a polymeric layer, which is also arranged between the glass panes and connects them to one another. The polymeric layer can, for example, be present as a film between the two glass panes, but it is also possible to initially apply the polymeric layer in liquid form, with the polymeric liquid hardening to form a polymeric layer when the two glass panes are connected.

The mechanical resistance or quality of the composite is usually checked in the so-called “pummel test”. In general, when the composite is destroyed, which can also be referred to as “laminated safety glass”, the glass fragments stick to the polymeric layer for example designed as a PVB film, must remain stuck between the glass panes of the composite. This is checked with the “pummel test”, in which a laminated glass comprising two panes of glass with a maximum thickness of 2 * 4 mm is worked on an inclined metal base with a hammer (to pummel = hit). The glass is destroyed by mechanical impact. The visual assessment is then carried out. The adhesion level is divided into “pummel values” between 0 and 10 for each exposed film area or exposed area of the polymeric layer, with higher values indicating better adhesion of the glass fragments to the polymeric layer.

If the polymeric layer is designed as PVB, the sample is first cooled to -18°C, otherwise the glass fragments would be pressed into the polymeric layer. If the glass panes in the sample are float glass panes, both glass plates of the laminated glass are tested. It has been shown that so-called “tin bath sides” deliver worse values in the pummel test than the fire sides, i.e. the side of the glass pane formed at the top using the float process.

Examples

The invention is explained in more detail below using examples.

The glass sheet according to the present disclosure includes a glass comprising SiO ₂ and B ₂ O ₃ .

According to a first exemplary embodiment, the glass can be given by a composition having the following components, each given in% by weight on an oxide basis: _SiO2 60 to 85, particularly preferably up to 82 _{B2O3 _} 7 to 26 _{Al2O3 _} 0 to 12, preferably greater than 0 to 11, particularly preferably up to 7 _Li2O 0 to 1 Well ₂ O 0.5 to 6 _K2O 0 to 3 MgO 0 to 6 CaO 0 to 5 SrO 0 to 4 ZnO 0 to 3 _ZrO2 0 to 3.

Other components that are commonly used in glass production can also be included, for example refining agents. These are usually included in a content of no more than 2% by weight of the glass.

For the following compositions, deviations of 100% in the total weight percentage may occur due to analysis-related rounding errors.

An exemplary glass is given in the following composition range in wt.% on an oxide basis: _SiO2 75 - 85 _{B2O3 _} 10-15 _{Al2O3 _} 1-3 Well ₂ O 2-5 _K2O 0-1 NaCl less than 0.5

An exemplary composition of a glass in this composition range in wt.% based on oxide is given as follows: _SiO2 80.8 _{B2O3 _} 12.7 _{Al2O3 _} 2.4 Well ₂ O 3.5 _K2O 0.6 NaCl 0.1

Another glass is given in the following composition range in wt.% based on oxide: _SiO2 73-83 _{B2O3 _} 8-12 _{Al2O3 _} 1-4 Well ₂ O 2-4 _K2O 1-3 MgO 1-3 CaO 1-3

Another exemplary composition of a glass in this composition range in wt.% based on oxide is given as follows: _SiO2 78.1 _{B2O3 _} 9.8 _{Al2O3 _} 2.5 Well ₂ O 2.8 _K2O 2.5 MgO 1.8 CaO 2.5

Such glasses in the composition range mentioned above, in particular with the specific compositions mentioned above as examples, are advantageous because they not only have thermal expansion coefficients, which are advantageously between 2 * 10 ^-6 /K and 6 * 10 ^-6 /K, depending on precise composition, but also because they can have sufficient mechanical resistance, for example to surface loads.

• In einem nach unten geöffneten Behälter befinden sich Splittteilchen, welche aus dem Behälter in ein Freifallrohr eintreten und dieses nach einer Freifallstrecke in Richtung auf eine Scheibe verlassen konnten, auf welche die Splittteilchen mit jeweils einem definierten Teilchenimpuls P_r(iesel) auftreffen, der durch die jeweilige Teilchenmasse und die entlang der Freifallstrecke F gewonnene Geschwindigkeit V_max definiert wird.

In particular, with such compositions it is also possible to obtain a glass pane which has only a slight scattering in the uncoated area according to a so-called chip trickle test. The grit trickle test is carried out as briefly explained below:

• In a container that is open at the bottom there are chipping particles, which enter from the container into a free-fall tube and can leave this after a free-fall distance in the direction of a disk, on which the chipping particles each impact with a defined particle impulse P _{r (iesel)} , which is transmitted through the respective particle mass and the speed V _max obtained along the free fall distance F is defined.

To avoid adhesions, the grit particles are dried before carrying out the grit trickle test, so that it is ensured that only a single particle hits the disc, independent of other particles and non-coherent particle agglomerates.

The disk can each be arranged at a different angle of inclination α', this angle of inclination α' being the angle to a horizontal plane to which the chippings move perpendicularly until they hit the disk.

The grit trickle test described above is carried out for a defined inclination angle α' until a - previously defined - total amount of grit particles has hit the disc.

The damage to the glass surface caused in this test leads to scattering/or Haze), which can be determined using measurements. This measurement of the Haze/dr scattering is preferably carried out in accordance with ASTM D1003 (CIE C) with an appropriately calibrated Haze measuring device, for example the Haze-Gard plus AT-4725 device from BYK-Gardner. In particular, glass panes that can be used here are those that have a haze value of less than 6% in the uncoated area according to the chip trickle test as described above, preferably for values for the inclination angle α 'between 15° and 60°.

Glass panes comprising such glasses can, particularly advantageously, have a strength of between 100 MPa and 210 MPa, preferably at most 200 MPa, when uncoated.

• - Hydrolytische Beständigkeit gemäß ISO 719 / DIN 12 111 HGB 1; gemäß ISO 720 = HGA 1, d.h. je nach durchgeführter Testung steht H entweder für HGA oder HGB.
• - Säurebeständigkeit gemäß DIN 12 116 ; kann aber auch durchgeführt werden nach ISO 1776, wobei dann hier Werte von ≤ 100 µg Na₂O je 100 cm² erhalten werden.
• - Laugenbeständigkeit gemäß ISO 695 / DIN 52322 ; hier wird die Klasse A2 erhalten.

Such glasses preferably have very high chemical resistance. These can be differentiated, for example, into acid (S), alkali (L) and hydrolytic (H) resistance. The resistance, given in classes H, S, L, is preferably H = 1, S = 1, L = 1 - 3 according to one embodiment. The chemical resistance is determined in accordance with the following standards:

• - Hydrolytic resistance according to ISO 719 / DIN 12 111 HGB 1; according to ISO 720 = HGA 1, i.e. depending on the testing carried out, H stands for either HGA or HGB.
• - Acid resistance according to DIN 12 116 ; but can also be carried out according to ISO 1776, whereby values of ≤ 100 µg Na ₂ O per 100 cm ² are obtained.
• - Alkaline resistance according to ISO 695 / DIN 52322 ; Class A2 is maintained here.

Common ceramic color bodies can be used as pigments, in particular spinel-based pigments, such as chrome-copper spinels, iron-nickel-chrome spinels or ferrite or hematite. Other oxides, such as iron-manganese oxides or iron-chromium oxides, can in principle also be used, for example TiO ₂ . Usual pigment sizes can range from an average of 0.15 µm to 5 µm, whereby the d ₉₀ value, based on the equivalent diameter, can be up to 15 µm. However, finer particle sizes may be preferred because they are easier to print.

Additives can generally be, for example, foaming agents. Foaming agents can also be referred to generally as blowing agents or pore formers within the scope of the present disclosure. In particular, starches such as corn starch, rice starch, wheat starch, potato starch or cassava or mixtures thereof can be used as foaming agents. It is also possible to use sugar for this, for example maltose, glucose, fructose and/or sucrose or mixtures thereof. The starches mentioned decompose at temperatures around 200°C; The sugars, on the other hand, at lower temperatures between approx. 100°C and 150°C, depending on the exact compound.

Alternatively or additionally, fillers can also be used as additives. These have an average grain size from the nm range to the µm range. Furthermore, it is pointed out that the coating according to the disclosure and the corresponding paste comprise at least one filler.

In particular, silicas, for example pyrogenic or precipitated silicas, with particle sizes of less than 1 μm, for example only 0.1 μm or even less, for example only 0, can generally be used as the at least one filler and optionally also as a further filler or further fillers. 04 µm, and different surfaces depending on the manufacturing process. Silicas are therefore advantageous because they have very low thermal expansion coefficients of around 0.5 * 10 ^-6 /K. It is also possible to use negatively expanding fillers, such as cordierite or β-eucryptite (which has a thermal expansion coefficient of -1.1 to -6.5 * 10 ^-6 /K). Such fillers can, for example, have particle sizes of around 1 μm or more, for example 1.5 μm or 1.2 μm.

Other fillers are, for example, round particles with grain sizes, preferably based on the equivalent diameter, in particular the volume equivalent equivalent diameter, preferably on the d ₅₀ value of the equivalent diameter, between 1 and 20 μm, preferably between 1 and 5 μm, so these do not protrude from the final coating. For example, this can be achieved by means of a quartz glass filler comprising spherical particles, such as the filler used as an example in the context of the present disclosure, in which the particles have diameters between 1 μm and 5 μm. This is a highly pure, spherical quartz glass. In principle, other quartz, quartz glass and quartz precursor spheres can also be used as fillers.

It is also possible to use special, porous fillers. For example, porous glasses, such as those available under the name “CoralPor®”, and porous crystalline materials are preferred. The fillers sold under the “CoralPor” brand and used here are borosilicate glasses that have been thermally and chemically treated in such a way that open porosity is specifically adjusted. In general, it is generally possible to use nano- and macroporous multicomponent glasses with a low expansion coefficient and which have a rigid amorphous microstructure as porous glasses. In principle, other low-stretch porous glass powders are also suitable, not just the CoralPor® products used here as an example. An example of porous crystalline materials are those based on zeolites.

The filler can also be formed in-situ, for example by decomposition of an organometallic or organosilicon component. This was shown here as an example by adding the silicone resin, which is sold under the Silres® brand. This is a silicone resin that converts to SiOC when heated, resulting in a grayish filler. In principle, in addition to Silres®, other decomposing silicone resins are also suitable.

Some exemplary frit compositions are compiled below. The components are stated in the following table in % by weight on an oxide basis. Other components that are commonly used in glass production can also be included, for example refining agents. These are usually included in a content of no more than 2% by weight of the glass. Example 1 2 3 4 5 6 7 8th 9 10 11 _{Al2O3 _} 8.2 7.2 5.4 0.6 5.9 0.10 1.00 5.1 5.3 5.0 2.0 _{B2O3 _} 18 22.8 24.0 24.6 21.5 15.70 12.75 21.9 22.9 23.4 8.3 BaO _{Bi2O3 _} 14 10.0 10.0 11.0 43.25 CaO 1.3 1.2 0.5 0.5 0.1 CoO 2.9 _K2O 0.1 1.7 1.8 0.8 1.75 _Li2O 3.2 4.4 4.9 0.8 0.8 4.8 0.8 MgO 0.3 Well ₂ O 5.2 1.2 0.2 6.1 2.4 2.5 2.75 _SiO2 55 55.6 56.0 66.6 58.0 32.70 24.25 63.4 66.2 55.0 29.5 SrO 1.0 _TiO2 1.6 ZnO 0.4 3.3 51.50 62.00 8.9

Below are some first coat coating compositions and some paste compositions.

Coatings produced, in particular first coatings with these frit compositions, showed that either a low pigment content (<7.5% by volume) or a higher pigment content (≥20% by volume) can be advantageous for the mechanical properties of the pane that is at least partially coated . In the first case, the α-mismatch, thus the difference in the thermal expansion coefficients, between the coating, in particular the first coating, and the glass pane is advantageous; in the latter, pores form in the coating, in particular in the first coating tion, which are advantageous up to a pigment content of 37.5% by volume. Thereafter, the coating is generally too porous for the purposes of the present invention.

In the context of the present disclosure, the bending tensile strength was determined using a double ring method in accordance with DIN 1288-5. The respective area of the glass pane subjected to the measurement was coated over its entire surface, so that uncoated areas of the glass pane had essentially no influence on the measurement results. In particular, the influence of the proportion of pigments on the bending tensile strength can be clearly seen from this figure.

Surprisingly, adding low-stretch fillers leads to an increase in mechanical strength even at low additions. Addition of more than 30% by volume of low-stretch filler, which is not and therefore in particular not colored in the coating, leads to a reduction in the opacity/optical density below 1.5 at the thicknesses disclosed here for the coating and is regular for the application not suitable. This can be counteracted with more pigment content. This is shown as an example in the two tables below.

The following table shows compositions of coatings according to embodiments: No. Layer Vol.-% Layer wt% Frit pigment filler Frit pigment filler 1 1.25% vol extra filler 75.5 23.25 1.25 58.8 40.1 1.1 2 10% vol extra filler 69.5 21.4 9 55.5 37.9 6.6 3 Pigment variation + 10% vol. filler 76.5 13.5 10 66.2 26 7.8 4 Pigment variation + 10% vol. filler 65 15 20 55.8 28.6 15.6 No. Layer Vol.-% Optical density Frit pigment filler 5 Filler silica 75.6 23.2 1.2 2.9 6 Filler β-eucryptite 75.6 23.2 1.2 2.3 7 Filler porous glass 75.6 23.2 1.2 2.3 8th Filler β-eucryptite 66.55 20.45 13 1.7 9 Filler silica 66.55 20.45 13 1.4 10 Filler quartz glass ball 66.55 20.45 13 1.7 11 Filler silica 55 35 10 2.6 12 Filler silica 60 30 10 2.2 13 Filler silicone resin/SiOC 75.6 23.2 1.2 1.8 14 Filler silicone resin/SiOC 72.8 22.4 4.8 1.8 15 Filler silicone resin/SiOC 66.5 20.5 13 1.9 A Comparison 76.5 23.5 - 2.5 b Comparison 65 35 - 3

Such coatings can be obtained with pastes as listed in the table below (the numbering of the coating and paste corresponds to their production): Pastes (% by weight) Frit pigment filler medium 1 40.60 27.70 0.7 31.00 2 37.5 25.6 4.4 32.5 3 44.7 17.6 5.3 32.4 4 37.5 19.2 10.4 32.9

4 shows a corresponding representation of the results of measurements of the bending tensile strength on various glass panes coated according to the present disclosure, with different fillers, namely a fumed silica, β-eucryptite and CoralPor®, each with a proportion of 1.25 vol%, being used for the different measuring points . The bending tensile strength was determined using a double ring method in accordance with DIN 1288-5. The respective area of the glass pane subjected to the measurement was coated over its entire surface, so that uncoated areas of the glass pane had essentially no influence on the measurement results. In particular, the influence of the proportion of pigments on the bending tensile strength can be clearly seen from this figure.

It has been found that a filler content of greater than or equal to 1.0% by volume, based on the solids content, can be very advantageous in order to increase the strength of the glass pane compared to coatings that do not contain any filler. As stated, any optical density that may be too low if the filler content is present can be compensated for by increasing the pigment content.

In general, the filler content can be up to 20% by volume or even up to 25% by volume or even up to 27% by volume, again based on the total solids content of the coating. Furthermore, it has generally been shown that it can be advantageous if the pigment content of the coating is high compared to the filler used, for example the volume ratio of filler to pigment between 1: 2 and 1:5, preferably between 1:3 and 1: 4, is. Despite this ratio, it is surprisingly the case that the color coordinates of such layers do not deviate greatly from those in which a lower ratio of filler to pigment was set or in which no filler was added at all.

Particularly advantageous properties can be obtained if high contents of pigments, for example almost 40% by volume, are combined with medium contents of fillers, for example from 8 to 15% by volume of filler. This information generally refers to all pigments and fillers used, i.e. to the total pigment and filler content of the coating. In this way, the glass pane is advantageously particularly strong while, surprisingly, the resulting coating also has sufficient scratch resistance or abrasion resistance.

The following table lists some compositions of coatings according to embodiments that have proven to be particularly advantageous. The information in the table below refers to the volume of the resulting coating, so the information is given in % by volume. The fillers used were a fumed silica, β-eucryptite, a porous filler (CoralPor®) and the fillers quartz glass beads (d ₅₀ between 1 and 5 µm) and silicone resin (Silres ®) that decomposes into a solid (SiOC). No. Frit pigment filler Art Crowd 5 75.6 23.2 silica 1.2 6 75.6 23.2 β-eucryptite 1.2 7 75.6 23.2 CoralPor® 1.2 8th 66.6 20.4 β-eucryptite 13 9 66.6 20.4 silica 13 10 66.6 20.4 Quartz glass ball 13 11 55 35 silica 10 12 60 30 silica 10 13 75.6 23.2 silicone resin 1.2 14 72.8 22.4 silicone resin 4.8 15 66.5 20.5 silicone resin 13

By adding foaming agents or blowing agents, a targeted, closed porosity is introduced into the first coating. The pores must be small enough to remain in the selected layer thickness, this means in the selected thickness of the first coating and, in the further embodiment, the first thickness together with the thickness of the intermediate layer. Increasing the pore addition above 25% by volume leads to a crispy appearance and a reduction in opacity.

Description of the drawings

• 1 eine schematische und nicht maßstabsgetreue Darstellung eines Verbunds nach einer Ausführungsform, sowie
• 2 und 3 schematische und nicht maßstabsgetreue Darstellungen einer Glasscheibe nach einer Ausführungsform,
• 4 Ergebnisse von Messungen der Biegezugfestigkeit an verschiedenen gemäß der vorliegenden Offenbarung beschichteten Glasscheiben, wobei für die verschiedenen Messpunkte verschiedene Füllstoffe, nämlich pyrogene Kieselsäure, β-Eukryptit und CoralPor® jeweils mit einem Anteil von 1,25 Vol.-% verwendet wurden,
• 5 bis 9 Diagramme betreffend den Einfluss von Füllstoff- und Pigmentgehalten in Beschichtungen auf unterschiedliche Schicht- bzw. Scheibeneigenschaften, sowie
• 10 rasterelektronenmikroskopische Aufnahmen unterschiedlicher beschichteter Glasscheiben.

The invention is further explained below with reference to figures. Show it

• 1 a schematic and not to scale representation of a composite according to one embodiment, and
• 2 and 3 schematic and not to scale representations of a glass pane according to one embodiment,
• 4 Results of measurements of the bending tensile strength on various glass panes coated according to the present disclosure, different fillers, namely fumed silica, β-eucryptite and CoralPor®, each with a proportion of 1.25% by volume, being used for the various measuring points,
• 5 until 9 Diagrams regarding the influence of filler and pigment contents in coatings on different layer or pane properties, as well
• 10 Scanning electron micrographs of different coated glass panes.

1 is a schematic and not to scale representation of a composite or a laminated glass pane 10 according to an embodiment of the present disclosure. The composite 10 comprises two panes 1, 2, the pane 1 being a glass pane for a vehicle according to an embodiment of the present disclosure. Pane 2 is another pane of glass and can, for example, consist of soda lime glass or the glass of pane 1 disclosed here. A polymeric layer 3 is arranged between the two glass panes 1, 2 and, here in the edge region of the composite 10, the coating 11. This is arranged on one side (not designated) of the glass pane 1 and can be the first coating in the context of the following description or comprise the first coating together with the further coating as an intermediate layer.

For reasons of better illustration, the coating 11 was shown here as thick, i.e. in comparison with that of the two panes 1, 2; However, as stated, this is purely for better presentation. The coating 11 is generally significantly thinner than each of the two disks 1, 2 and generally also thinner than the polymeric layer 3. The polymeric layer 3 can also be a film.

As can be seen, the composite 10 is designed here as a curved laminated glass pane, such as can also be used as a windshield. In general, without limitation to the in 1 Example shown, however, it is also possible that the composite 10 does not include any curved disks 1, 2, but is flat. It is also possible for the curvature of the composite 10 to be the opposite of that in 1 shown illustration. In the example of 1 the glass pane 1 would be the outside of a windshield, but it is also generally possible that the glass disc 1 is arranged on the inside of a windshield. In any case, however, the coating 3 is arranged between the two glass panes 1, 2.

An arrangement like in 1 but can be advantageous since the glass pane 1 comprises SiO ₂ and B ₂ O ₃ as components of the glassy material. Such borosilicate glass is more scratch-resistant than, for example, soda-lime glass, so it can be advantageous if the glass pane 1 is as in 1 shown in the composite 10 is designed so that it points “outside”, i.e. would point outwards in the case of use as a windshield. This would provide better protection against stone chips and similar mechanical stresses.

To illustrate the structure of the glass pane 1 according to embodiments, this is shown in the 2 and 3 each presented in the form of a schematic and true-to-scale illustration. 2 shows a side view. Here, however, the glass pane 1 is not yet curved. In general, without limitation to the in 1 shown example of a glass pane 1, it is also possible that the glass pane is curved. However, it can be advantageous if a flat, non-curved disk 1 is initially used, which is then later bent, for example in a thermal process. Here too, for reasons of better representation, the thickness of the coating 11 is shown to be significantly larger than in reality.

The arrangement of the disk 1 corresponds to that in 1 , as stated except that the disk in 2 is not curved. As can be seen, the coating 11 is formed here on the side 102, which faces the second pane 2 in the composite 10. The polymeric layer 3, which is arranged in the composite between the disk 1 and the disk 2, is not shown here. It is expressly pointed out here that the polymeric layer 3 both directly contacts the side 102 of the disk and is arranged on the coating 11 arranged in the area (or areas) of the disk 1 (or the side 102 of the disk 1). .

The coating 11 is arranged here in the edge area of the pane 1, in the illustration 2 each left and right. Here, for example, it may be that the coating is applied overall in the form of a “frame”.

For this purpose, refer to the 3 referred to, which also shows a schematic and not to scale illustration of a top view of a pane 1 according to one embodiment. The coating 11 is here designed as a frame running around the edge of the pane 1, the coating initially being designed to be opaque, i.e. as a layer without interruptions, and passing towards the center of the pane 1 via a grid or dot pattern 111 into the uncoated area . If the pane 1 is used in a composite 10, this uncoated area is the visible area of, for example, a windshield. Of course, it is generally possible that the frame is not as uniform as shown schematically in 3 shown, but for example has bulges, as is often the case with windshields in the area of the rear-view mirrors.

5 shows the influence of the filler content for different fillers on the average modulus of rupture of the coated glass panes. As can be seen, even a small addition of just 1.2% by volume already results in an improvement in the modulus of rupture, i.e. its increase, compared to coatings that do not contain any filler, i.e. only glass flow/binder and pigment . Surprisingly, it turns out that adding silica can be particularly advantageous, especially in relatively high levels of 13% by volume. This is particularly surprising in comparison with a filler such as β-eucryptite, which has a particularly low coefficient of thermal expansion (even in the negative range). It would have been assumed that such a negatively expanding filler such as β-eucryptite should particularly easily help to keep the resulting coefficient of thermal expansion of the coating, in which the pigments, which have a relatively high degree of expansion compared to the glass substrate, should ideally be evened out, as low as possible hold or adapt to that of the glass substrate. However, the positive effect of such particularly low-stretching fillers (or even negatively stretching fillers) is apparently surprisingly less great than expected. This also applies in a corresponding way to porous glass beads such as “CoralPor®”, which were also previously considered to be potentially very favorable for the resulting thermal expansion and, due to the inherent porosity, also for balancing thermally induced stresses.

6 shows the influence of fillers and filler contents on the optical density, determined through the pane. As you can see, adding filler can actually improve the optical density, especially if only a small amount of filler is added. This could possibly be due to a better distribution of the pigment particles in the coating, which could possibly be caused by small amounts of fillers. However, this obviously depends on the type of filler added. However, for most of the fillers examined and especially higher filler contents, the addition of filler is associated with a decrease in the optical density, although this is still considered sufficient.

7 shows schematically the influence of pigment and filler content on the resulting average modulus of rupture. In general, higher levels of pigments and higher levels of fillers (the filler used here being a silica) also lead to higher moduli of rupture.

8th shows for the in 7 With regard to the resulting modulus of rupture, samples examined the influence of filler and pigment content of the coating on the optical density. This shows that up to filler contents of around 10% by volume, the influence on the optical density is still acceptably low and that the negative effect on the optical density already described only occurs at higher filler contents. At low filler contents, as already discussed, at least for the filler considered here, silica, there is even an increase in the optical density.

9 shows the influence on the resulting color coordinates of the coating for different pigment and filler contents. The influence on the resulting color of the coating is very small, so that even in the “achromatic range” of the color coordinates a* and b* considered here, only very small and non-systematic deviations occur. This also applies to quite high filler contents of 13% by volume.

10 shows the layer formation for different coatings. At the top left and at the very bottom left you can see two coatings which, in addition to the glass flow, only contain pigment, and in different colors. The coating shown at the bottom left, which contains 23% vol. pigment, shows a smooth, dense coating, whereas higher pigment contents result in a layer that is up to 4 µm thick, slightly porous and, above all, unevenly thick. Coatings in the middle range of 10 include 23% by volume of pigment and 15% by volume of a filler. While the quartz glass filler (d ₅₀ between 1 and 5µm) leads to a very unstable layer structure, which results in low scratch resistance simply because individual components of the coating protrude, the silicone-based fillers of the “Silres@” coating lead to one smooth layer with evenly distributed pores, which are created by the burning out of the organic components of the filler. However, the coating has obviously become unstable due to the evenly distributed pores and is therefore unfavorable in terms of mechanical layer stability.

However, there are particularly great advantages with a coating like the one at the top right 10 is shown, connected. The filler used, a silica, leads to non-binder contents of even more than 37% by volume (i.e. comparable to the coating in the upper left area of 10 with 35 vol.% pigment) nevertheless and very surprisingly results in a smooth layer formation, comparable to a layer with significantly less particulate content (like the coating with 23 vol.% pigment at the bottom left). However, the addition of filler here is associated with the formation of a graded porosity, which increases precisely to the interface between the coating and the glass pane. The inventors suspect that it is precisely this gradient of porosity that results in a particularly favorable design, so that the coating is still sufficiently scratch-resistant, but still results in a high mechanical strength of the coated glass pane.

Reference symbol list

1

glass pane

10

Composite, composite disc

11

Coating

101, 102

sides of the glass pane

111

Dot grid

2

Another pane of glass

3

Polymeric layer

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2015/059406 A [0005]
• WO 2017/157660 A1 [0006]
• WO 2019/130285 A1 [0008]
• WO 2018/122769 A1 [0009]
• EP 3022164 B1 [0045]

Non-patent literature cited

• DIN 12 111 [0124]
• DIN 12 116 [0124]
• DIN 52322 [0124]

Claims (9)

Glass pane, in particular partially coated glass pane for a vehicle, comprising a glass comprising SiO ₂ and B ₂ O ₃ , comprising at least one coating applied in at least one region of at least one side of the glass pane with a first coating, the first coating comprising at least one binder comprising SiO ₂ , at least one pigment and at least one additive, wherein the glass pane has a bending strength between at least 5 and at most 170 MPa, preferably at least 20 and at most 170 MPa, in the at least one area which has the applied first coating on the at least one side of the glass pane , particularly preferably at least 35 MPa, very particularly preferably at least 60 MPa, and most preferably at least 80 MPa, and wherein the binder is glass-based and is designed as a glass frit and the coating is designed as an enamel layer and the additive is a filler. glass pane Claim 1 , wherein the filler is a filler with a linear thermal expansion coefficient between -10 * 10 ^-6 /K and +10 * 10 ^-6 /K, preferably between -8 * 10 ^-6 /K and +5 * 10 ^-6 /K , particularly preferably between -6.5 * 10 ^-6 /K and +3 * 10 ^-6 /K. Glass pane after one of the Claims 1 until 2 , having at least one of the following features: - in at least a partial area or within the entire at least one area of the at least one side of the glass pane, a further coating, in particular an intermediate layer, is arranged between the glass pane and the first coating, - the first coating comprises between 0 .5% by volume and 50% by volume of pigment, preferably 0.5 - 40% by volume of pigment, particularly preferably between 20 and 40% by volume of pigment, and between 99.5% by volume and 50% by volume. -% glass frit, - the glass of the glass pane has a linear thermal expansion coefficient between 2 * 10 ^-6 /K and 6 * 10 ^-6 /K, - the glass of the glass pane comprises at least 60% by weight of SiO ₂ to a maximum of 85% by weight .% SiO ₂ and/or at least 7 wt.% B ₂ O ₃ to at most 26 wt.% B ₂ O ₃ , - the first coating has a linear thermal expansion coefficient between at least 3 * 10 ^-6 /K and at most 10 * 10 ^-6 /K, preferably less than 9 * 10 ^-6 /K, - the glass pane has a thickness between at least 1 mm and at most 12 mm. Glass pane after one of the Claims 1 until 3 , wherein the first coating comprises a further additive, the further additive being a blowing agent or a filler. Glass pane after one of the Claims 1 until 4 , wherein the glass frit comprises a coloring component, and/or wherein the proportion of the pigment in the coating comprises at most 40% by volume, preferably at most 20% by volume. Paste for producing a coating on a glass pane, preferably a glass pane that is at least partially coated according to one of the Claims 1 until 5 , comprising - at least one glass-based binder, preferably a glass frit, - at least one pigment, - at least one additive which is designed as a filler, - a medium, wherein the glass frit comprises a glass comprising at least the following components in% by weight based on oxide: _SiO2 10 to 70 _{B2O3 _} 10 to 26 _{Al2O3 _} more than 0 to 9. Paste after Claim 6 , having a viscosity, preferably determined using a plate viscometer, between 1500 and 8000 mPas, preferably between 2000 mPas and 6500 mPas and particularly preferably between 2500 mPas and 5000 mPas. Paste according to one of the Claims 6 or 7 , having at least one of the following features: - The paste comprises between 0.5% by volume and 50% by volume of pigment, preferably less than 40% by volume of pigment, and between 50% by volume and 99.5% by volume .-% glass frit, based on the solids content comprised by the paste, - The glass frit has a linear thermal expansion coefficient between at least 2 * 10 ^-6 /K and at most 10 * 10 ^-6 /K, preferably between at least 3 * 10 ^-6 /K and at most 8.5 * 10 ^-6 /K, - the paste comprises a further additive, the further additive being a blowing agent or a filler, the additive preferably being a filler with a linear thermal expansion coefficient between -10 * 10 ^{- 6} /K and +10 * 10 ^-6 /K, - the glass frit comprises a coloring component, and / or the proportion of the pigment in the coating is at most 40% by volume, preferably at most 20% by volume. Composite comprising a glass pane according to one of the Claims 1 until 5 and another glass pane, the coating preferably being arranged between the glass panes.

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