Glass article, method for manufacturing thereto and motor vehicle glazing unit comprising such a glass article

Description

Previous technique

[0001] The invention relates to the field of glazing, in particular glazing for motor vehicles, for example windshields, rear windows, side windows, quarter windows or roofs.

[0002] Automotive glazing must meet a large number of requirements, in terms of both safety and comfort.

[0003] Such glazing is often monolithic, comprising a single sheet of thermally tempered glass.

[0004] Alternatively, and to improve both safety and acoustic comfort, a growing number of windows are laminated glass, meaning they consist of two sheets of glass bonded together with a lamination interlayer. This interlayer not only holds glass fragments together in case of breakage, but also provides other benefits, particularly in terms of burglary resistance and improved acoustic properties.

[0005] Layers of enamel, usually black and opaque, are often applied to part of the glazing, generally as a peripheral band designed to protect the polymer seals used to fix and position the glazing in the bodywork openings from ultraviolet radiation. These layers also conceal the seals and other elements on the glazing, such as electrical connections or collector strips.

[0006] An enamel is a mineral layer formed by firing an enamel composition comprising a glass frit, especially bismuth borosilicate glass, and pigments.

[0007] In an effort to differentiate vehicles through design, automakers are also seeking original decorative elements, particularly those visible from the exterior, without compromising safety or the occupants' comfort in terms of lighting and temperature. Designs that create a smooth transition between the bodywork and the visible interior are especially desirable.

[0008] Dichroic materials are known for their property of reflecting incident light into reflected radiation of different wavelengths.

[0009] For example, in US patent 2010 / 0330339 A1, decorative glass is produced by depositing a dichroic film with an irregular surface. The film reflects or transmits light of different colors in patterns defined by the irregularity of the surface it covers, its design, and the angle of observation.

[0010] CN 102725663 B describes a dichroic coating that can be applied to a glass component of an electronic device to improve its aesthetics. Several methods can be used for this purpose, including depositing a layer of ink on the glass in addition to a dichroic material.

[0011] Alternatively, US patent 6,531,230 B1 proposes a polymeric film comprising layers with different optical properties, enabling the production of colored mirrors and polarizers. This film is characterized by a particularly uniform color variation depending on the viewing angle.

[0012] In addition, documents WO 2005 / 068385, WO 2020 / 064940 and EP 3 730 841 describe coatings comprising several layers of pigmented enamel. Description of the invention

[0013] The present invention therefore proposes, in order to obtain decorations enabling the creation of a smooth transition zone between the bodywork and the view in the field of automotive glazing, to implement such materials.

[0014] To describe such a transition, we speak of a "seamless" effect.

[0015] Accordingly, and in a first aspect, the invention relates to a glass article comprising: a glass substrate, a first layer covering at least partially the glass substrate and comprising at least one pigment chosen from dichroic pigments and metallic pigments, the first layer comprising 5% to 15% by weight of pigment(s) chosen from metallic and dichroic pigments, relative to the total weight of the first layer, and a second layer covering at least partially the glass substrate, substantially covering the entire surface of the first layer and comprising at least one black pigment.

[0016] In this glass article, different colors are achieved depending on the metallic and / or dichroic pigments used. The color, and therefore the pigments used, are chosen according to the color of the car body with which the "seamless" effect is desired.

[0017] Such a glass article according to the invention is particularly advantageous because it also allows for different colors to be obtained depending on the viewing angle. This characteristic, linked to the first layer of a glass article according to the invention, allows for better matching of the glazing to a vehicle body. Indeed, since car bodies in the automotive industry are also metallic, their color also depends on the viewing angle.

[0018] In addition, this first layer also gives a metallic appearance to the glazing, which contributes to the "seamless" effect obtained with the bodywork of a vehicle.

[0019] In one embodiment of the invention, this effect is sought at the level of a front windshield or a rear window of a vehicle, in contact with a bodywork element, in order to mitigate the visual transition between these two elements of the vehicle.

[0020] In another embodiment, a glass component according to the invention is used to replace metal parts commonly used in vehicles at the interfaces between the glazing and the body. Such parts are found, in particular, between the side windows and the doors or between the quarter windows and the quarter panels. A glass component according to the invention, used as a side or quarter window, thus eliminates the need for these metal parts in a vehicle by occupying the space where they are usually located, thereby achieving a seamless effect between the vehicle's body and glazing.

[0021] The glass substrate suitable for a glass article according to the invention can be a sheet of mineral glass, optionally thermally tempered or chemically strengthened, in particular chosen from sheets of float glass, soda-lime glass, aluminosilicate and borosilicate glass.

[0022] Preferably, the glass substrate in a glass article according to the invention is a sheet of soda-lime silico-glass.

[0023] Dichroic pigments, known as "dichroic pigments", are known to those skilled in the art and described, for example, in patent EP 0 736 073 B1, referring to US patents 4,434,010; US 4,704,356; US 4,779,898; US 4,838,648; US 4,930,866; US 5,059,245; US 5,135,812; US 5,171,363 and US 5,214,530.

[0024] These pigments generally exhibit an interference structure comprising at least one metallic reflective layer and at least one dielectric transparent layer. This interference structure produces the dichroic effect, typically via a dielectric stack of layers having different refractive indices or by the combination of transparent dielectric layer(s) and semi-opaque metallic layer(s).

[0025] The metallic reflective layer is usually made of aluminum, but can also be made of gold, copper, or silver.

[0026] The semi-opaque metallic layer can be formed from metals such as chromium, nickel, or an alloy based on nickel, chromium, and iron.

[0027] The transparent dielectric layer can be formed from silica, magnesium fluoride, or aluminum oxide.

[0028] The thickness of the layers varies depending on the desired characteristics of the pigment.

[0029] Suitable dichroic pigments for the invention may be, for example, Ocean Blue pigments Artikel 201003 and / or Magic Sapphire pigments Artikel 201006 marketed by Ceramic Colors.

[0030] The second layer of a glass article according to the invention fulfills several roles. It provides both mechanical protection, in particular scratch resistance, and support for the first layer. Furthermore, since this second layer contains a black pigment, it enhances the dichroic effect of the first layer by contrast.

[0031] In this text, the term "overlaying" means physical contact between the covered and overlaying layers. Thus, in the sense of the invention, the first layer is in contact with the glass substrate and the second layer is in contact with both the glass substrate and the first layer.

[0032] Thus, in a preferred embodiment, the glass article according to the invention does not include any optically active layer between the glass substrate and the first layer, or when the second layer is in contact with the glass substrate, between the glass substrate and the second layer.

[0033] In a particular embodiment of the invention, the first layer comprises at least one pigment selected from dichroic pigments.

[0034] In another embodiment of the invention, the first layer comprises at least one pigment selected from metallic pigments.

[0035] Such pigments are chosen for example from mica and titanium rutile pigments such as those sold under the references Iriodin and Xirallic by the company Merck.

[0036] A first layer suitable for the invention can, for example, be obtained by adding pigments suitable for the invention to a transparent enamel composition.

[0037] A first layer containing such pigments can also be obtained, for example, from the enamel compositions sold under references 154030, 164030, 174030, 194030 and 134030, and preferably 194030 and 134030, by the Vibrantz company. These compositions correspond respectively to metallic silver, copper, red, matte silver and gold colorations.

[0038] The first layer of a glass article according to the invention may comprise a mixture of dichroic pigments and metallic pigments.

[0039] A first layer suitable for the invention may contain from 7% to 13% by weight; and preferably 10% by weight of pigment(s) chosen from metallic and dichroic pigments, relative to the total weight of the first layer.

[0040] A first layer containing at least 5% by weight of pigment(s) suitable for the invention allows obtaining a particularly satisfactory "seamless" effect.

[0041] A first layer containing at most 15% by weight of pigment(s) suitable for the invention has a viscosity particularly suitable for printing, in particular by screen printing, on a glass substrate.

[0042] The pigments included in the first layer of a glass article according to the invention generally have a size of 5 to 40 µm. A particle size of up to 120 µm may also be suitable for the invention, particularly to enhance the visual effect produced by the pigment, but requires the use of suitable screens with a high mesh opening to implement a screen printing process as described below.

[0043] The first layer of a glazing according to the invention can be woven.

[0044] The screen-like pattern of the first layer allows the second, black layer to be seen through the perforations in the first layer during vehicle installation. The contrast between the two layers enhances the aesthetic appeal of the glazing, particularly by accentuating the dichroic effect.

[0045] In a glass article according to the invention, the thickness of the first and second layers can be from 1 µm to 100 µm, in particular from 10 µm to 80 µm and preferably from 15 µm to 50 µm.

[0046] The first and second layers may also include a glass frit.

[0047] In one particular embodiment, these layers correspond to glazes, comprising a glass frit, pigments, and an organic medium before firing, and then pigments and a vitreous matrix obtained by fusing the glass frit after firing. The term "glaze" refers to the layer both before and after firing. These glazes are typically obtained by firing above 500 °C.

[0048] The glass frit and / or the glass matrix is ​​preferably made of zinc and / or bismuth borosilicate glass. Preferably, the glass frit and / or the glass matrix is ​​bismuth silicate.

[0049] In the second layer, at least one black pigment is specifically based on an oxide or sulfide of iron, chromium, copper, cobalt, and / or manganese. Preferably, the black pigment is copper chromate.

[0050] According to another aspect, the present invention relates to a method for obtaining a glass article as defined above, comprising a step of printing the first layer onto the glass substrate; and a step of printing the second layer onto the first layer and the glass substrate.

[0051] In one embodiment of the invention, the printing steps are carried out by screen printing and / or by digital printing.

[0052] A screen printing process involves depositing a paste-like liquid onto a substrate, typically using a squeegee, through the mesh of a screen printing screen. The screen mesh is blocked in the areas of the substrate that must remain uncovered, so that the paste can only pass through the screen in the areas to be printed, according to a predefined pattern. The selective blocking of the mesh is therefore performed in reverse of the pattern to be printed.

[0053] This selective sealing is generally achieved by applying a photocurable resin to the screen and then exposing the parts of the screen to be sealed to ultraviolet radiation.

[0054] Selective exposure is for example achieved using a slide comprising a transparent support, typically made of polyester, coated with an opaque ultraviolet ink deposited according to the pattern to be printed.

[0055] The screen mesh is chosen according to the viscosity and surface tension of the paste as well as the desired thickness for the resulting layer of the screen printing deposition.

[0056] The screens used for screen printing the first and second layers can include from 30 to 100 threads per centimeter, for a thread diameter of 30 to 60 µm.

[0057] The screens used for first-layer screen printing must have a relatively large mesh opening, which translates into a maximum thread count. Therefore, first-layer screen printing can have up to 75 threads per centimeter, particularly up to 70 and preferably 68.

[0058] In particular, the screens used for the first layer comprise 40 to 70 threads per centimeter, for a thread diameter of 40 to 60 µm.

[0059] Preferably, the screens used for the first layer comprise 68 threads per centimeter, for a thread diameter of 55 µm.

[0060] To achieve an even higher mesh opening and prevent any clogging of the fabric, preferably, the screens used for the first layer include up to 49 threads per centimeter.

[0061] The screens used for screen printing the second layer must allow a deposit thick enough to cover the first layer and completely encapsulate the pigments contained in that first layer.

[0062] In particular, the screens used for the second layer comprise 80 to 100 threads per centimeter, for a thread diameter of 30 to 50 µm.

[0063] Preferably, the screens used for the second layer comprise 90 threads per centimeter, for a thread diameter of 40 µm.

[0064] In another embodiment of the invention, the screens used for the second layer comprise 45 to 65 wires per centimeter, with a wire diameter of 55 to 75 µm. Preferably, in this other embodiment, the screens used for the second layer comprise 55 wires per centimeter, with a wire diameter of 64 µm.

[0065] According to yet another aspect, the present invention relates to automotive glazing comprising a glass article according to the invention.

[0066] In a glazing according to the invention, the surface on which the first and second layers extend is called the "enameled zone".

[0067] The enameled area is presented in particular in the form of a peripheral band. That is to say, a band enclosed upon itself which, from each point of the glass article according to the invention, extends towards the interior of the glass article over a certain width, typically between 1 and 20 cm.

[0068] The remaining part of the automotive glazing according to the invention, called the "non-enameled area", is generally uncoated.

[0069] Alternatively, it can be coated with a stack of thin films, for example including a low-emissivity layer, notably silver-based or based on a transparent electrically conductive oxide such as indium tin oxide or doped tin or zinc oxides.

[0070] In a particular embodiment, the automotive glazing according to the invention is laminated or tempered glazing.

[0071] When the glazing according to the invention is laminated or tempered, the first and second layers can advantageously be deposited on the inner face of this glazing.

[0072] The term "inner face" refers to any face of a glass pane in the glazing that faces the interior of a vehicle. For example, in tempered glass, this could be the face in contact with the interior of the vehicle, or, in the case of laminated glass, the inner face of the outer pane, that is, the one located on the side of the lamination interlayer.

[0073] When the automotive glazing according to the invention is tempered, the tempering is advantageously carried out simultaneously with the curing of the first and second layers.

[0074] The automotive glazing according to the invention can be curved.

[0075] The glass substrate on which the first and second layers are deposited is generally flat. This is then preferably curved and therefore has a curved shape in the automotive glazing according to the invention.

[0076] The curvature of the glazing increases the impression of "seamlessness" for an observer. Indeed, compared to flat glass or glass with a less pronounced curve, observation from the same point results in a greater range of viewing angles and thus a greater range of glazing colours, since, as demonstrated in the examples below, this varies according to the viewing angle.

[0077] When the automotive glazing according to the invention is curved, the curvature thereof is advantageously carried out simultaneously with the curing of the first and second layers.

[0078] The glazing according to the invention may include an enameled area comprising 2 to 25%, in particular 3 to 20% and preferably 5 to 15% of the surface of its face coated by the first and second layers. Examples

[0079] The table below shows the configurations that were carried out and indicates in particular the percentage by mass of pigments in a layer in relation to the total mass of pigments in that layer. [Table 1] Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 First layer Mesh 68.55 Ocean blue Artikel 201003 from the company Ceramic Colors (%) 100 - 50 - - - Magic Sapphire Article 201006 from Ceramic Colors (%) - 100 50 - - - 194030 from the company Vibrantz (%) - - - 100 - 50 134030 from the company Vibrantz (%) - - - - 100 50 Viscosity (Pa·s) 8 ± 2 14 ± 2 Thickness (µm) 33 ± 2 24 ± 2 Second layer Ferro 14501 (%) 100 Viscosity (Pa·s) 13 ± 2 Thickness (µm) 35 ± 2 42 ± 2 Mesh 90.40 55.64

[0080] For each example, a sheet of glass was enameled by screen printing the first and second layers described in Table 1 above. In Examples 3 and 6, a homogeneous mixture of pigments was prepared before deposition.

[0081] A screen comprising 68 wires per centimeter and with a wire diameter of 55 µm was used for the deposition of the first layer.

[0082] A screen comprising 90 wires per centimeter and with a wire diameter of 40 µm was used for the deposition of the second layer for examples 1 to 3.

[0083] A screen comprising 55 centimeter wires and with a wire diameter of 64 µm was used for the deposition of the second layer for examples 4 to 6.

[0084] It should be noted that the thickness and viscosity measurements shown in Table 1 above were taken before the cooking stage.

[0085] After the coatings were applied, a drying time of 2 minutes at 150°C was observed. Then, the glass sheets bearing the two layers underwent a firing step at 650°C for 180 seconds.

[0086] The firing stage is carried out in a convection oven that replicates the conditions of an industrial process for the production of glass for the automotive industry. It has been observed that these conditions consistently produce the desired seamless effect.

[0087] The samples obtained were also convex. It was observed that the convexity has no influence on the materials used to produce a dichroic effect. This effect is therefore still obtained.

[0088] The reflection spectrum of Example 1, as well as its luminosity (L*), were measured at different angles using a spectrophotometer (Lambda 1050) with a Total Absolute Measurement System (TAMS) module that allows for rotation and simultaneous data acquisition. These measurements are presented in Table 2 below. [Table 2] -75° -60° -45° -30° -15° 15° 30° 45° 60° 75° RL (%) 27.62 10.25 6.01 5.08 4.97 4.98 5.06 5.89 9.75 25.61 L* 59.54 38.28 29.43 26.96 26.65 26.66 26.91 19.14 37.39 57.67 a* 0.09 0.35 0.07 -0.84 -1.44 -1.52 -0.9 0.05 0.33 0.06 b* 0.2 -0.4 -1.29 -1.6 -1.35 -1.52 -1.61 -1.36 -0.57 -0.08

[0089] The brightness (L*) varies from black (0) to white (100) while a* represents a colour ranging from green (negative) to red (positive) and b* represents a colour ranging from blue (negative) to yellow (positive).

[0090] Table 2 illustrates the clear variation in color and brightness of the sample depending on the viewing angle. It is also important to remember that in real-world use, this variation would be even greater because the viewing angle could vary in more than one direction.

[0091] It therefore appears that a glass article according to the invention makes it possible to cover a wide range of colours and is thus likely to match a bodywork element of a vehicle.

[0092] The inventors also noted that mixing two dichroic pigments, such as in examples 3 and 6 below, makes it possible to obtain an even higher number of colours on the same glass substrate, compared, respectively, to examples 1-2 and 3-4.

Claims

1. A glass article comprising: • a glass substrate, • a first layer at least partially covering the glass substrate and comprising at least one pigment selected from dichroic pigments and metal pigments, the first layer comprising from 5% to 15% by weight of pigment chosen from metallic and dichroic pigments, relative to the total weight of the first layer, and • a second layer at least partially covering the glass substrate, substantially covering the entire surface of the first layer and comprising at least one black pigment.

2. The glass article according to the preceding claim, wherein the at least one pigment comprised in the first layer is chosen from dichroic pigments.

3. The glass article according to any one of the preceding claims, wherein the first layer comprises a mixture of dichroic pigments and metal pigments.

4. The glass article according to any one of the preceding claims, wherein the first layer is screened.

5. The glass article according to any one of the preceding claims, wherein the first and second layers have a thickness of from 1 µm to 100 µm, in particular from 10 µm to 80 µm and preferably from 15 µm to 50 µm.

6. The glass article according to any one of the preceding claims, wherein the first and second layers further comprise a glass frit.

7. The glass article according to any one of the preceding claims, wherein the first layer comprises from 7% to 13% by weight; and preferably 10% by weight of pigment chosen from metallic and dichroic pigments, relative to the total weight of the first layer.

8. The glass article according to any one of the preceding claims, wherein the glass substrate is a sheet of mineral glass, optionally thermally tempered or chemically reinforced, in particular chosen from sheets of float glass, soda-lime-silica glass, aluminosilicate and borosilicate glass, and preferably is a sheet of soda-lime-silica glass.

9. The glass article according to any one of the preceding claims, wherein no optically active layer is included between the glass substrate and the first layer, or when the second layer is in contact with the glass substrate, between the glass substrate and the second layer.

10. A method for obtaining a glass article according to any one of the preceding claims, comprising: • a step of printing the first layer on the glass substrate, and • a step of printing the second layer on the first layer and the glass substrate.

11. The method according to the preceding claim, characterized in that the printing steps are carried out by screen printing and / or by digital printing.

12. An automotive glazing, characterized in that it comprises a glass article according to any one of claims 1 to 9.

13. The automotive glazing according to the preceding claim, said glazing being laminated or tempered.

14. The automotive glazing according to the preceding claim, wherein the first and second layers are arranged on the interior face.

15. The automotive glazing according to any one of claims 12 to 14, said glazing being curved.