Glass-ceramic substrate for a cooking device, glass-ceramic article, and production method

Abstract

The invention relates to a glass-ceramic substrate (12) for a cooking device, comprising a main surface (16) intended to receive cooking elements in direct contact therewith, the main surface (16) comprising a textured area (18), the textured area (18) having a peak density RPc less than or equal to 115 and an arithmetic mean deviation Ra greater than or equal to 1 µm and less than or equal to 6 µm. The invention also relates to a glass-ceramic article (10) comprising such a glass-ceramic substrate (12) and to a method for producing such a glass-ceramic substrate.

Description

DESCRIPTION TITLE: VITROCERAMIC SUBSTRATE FOR COOKING DEVICE, VITROCERAMIC ARTICLE AND MANUFACTURING PROCESS technical field

[0001] This paper concerns a glass-ceramic substrate for a cooking appliance. It also concerns a manufacturing process for such a substrate. Previous technique

[0002] It is known to texture a main face of a glass-ceramic substrate for a cooking device to give it anti-scratch, anti-adherence properties.

[0003] To this end, document FR3140623 describes a chemical texturing process for the surface of glass before ceramic heat treatment or for glass ceramics after ceramic heat treatment of glass.

[0004] Glass-ceramic substrates for cooking appliances are generally black and have a degree of light transparency to allow indicator lights to be seen. However, under certain lighting conditions, the electronic components of the cooking appliance can become visible by reflecting light from the light source positioned above the appliance.

[0005] To solve this problem, it has been proposed to deposit an opaque coating, such as a layer of paint, on the lower surface of the glass-ceramic substrate, that is to say on the surface opposite to the surface intended to receive cooking elements, such as pans and / or pots, in direct contact.

[0006] However, there is a risk of delamination of the opacifying coating, primarily due to differences in the coefficient of thermal expansion between the glass-ceramic and the opacifying coating. Furthermore, this coating application step complicates the manufacturing process of the glass-ceramic substrate.

[0007] There is also a need for a glass-ceramic substrate that is easy to manufacture and offers sufficient transparency for the user to to see the indicator lights without making the electronic components visible. Description of the invention

[0008] The present presentation aims to remedy at least some of these drawbacks.

[0009] To this end, the present presentation concerns a glass-ceramic substrate for a cooking device, comprising a main surface intended to receive cooking elements by direct contact, the main surface having a textured area, the textured area having a number of peaks RPc less than or equal to 115 and an arithmetic mean deviation Ra greater than or equal to 1 pm and less than or equal to 6 pm.

[0010] Since this is a glass-ceramic substrate, it is understood that we are not referring to a glass-ceramic substrate with a coating applied to it. Similarly, the textured area is not a coating applied to the substrate but rather an area created by treating the substrate itself. Therefore, there is no risk of delamination between the glass-ceramic substrate and a coating applied to it, particularly due to the difference in the coefficient of thermal expansion between the glass-ceramic substrate and the coating. This reduces the risk of defects appearing on the glass-ceramic article containing the glass-ceramic substrate. However, the textured area may include decorative elements applied to it, such as layers of enamel printed using screen printing.

[0011] The risks of chemical, thermal, mechanical and / or thermomechanical degradation are reduced because the glass-ceramic substrate is monolithic.

[0012] The risks of leaching of elements present in an additional layer and / or the risks of discoloration of the glass-ceramic substrate are reduced. The risks of leaching and / or discoloration can be due to chemical attack caused by hot or cold soiling and / or hot or cold cleaning products and / or thermo-oxidative reactions when the glass-ceramic substrate is heated.

[0013] The number of peaks RPc is defined in the DIN EN ISO 4287:2010 standard and measured over an evaluation length of 4 mm to 12.5 mm.

[0014] The arithmetic mean deviation Ra is defined in the DIN EN ISO 4287:2010 standard and measured over an evaluation length of 4 mm to 12.5 mm.

[0015] The textured area is substantially isotropic, meaning that the variation in the measurement of the number of RPc peaks varies little according to the direction of measurement.

[0016] It is understood that regardless of the measurement direction, the number of RPc peaks in the textured area is less than or equal to 115.

[0017] A number of RPc peaks less than or equal to 115 allows for a glass-ceramic substrate that reduces the visibility of the electronic components of a glass-ceramic article comprising the glass-ceramic substrate.

[0018] The scratch resistance of the glass-ceramic substrate improves with the value of the arithmetic mean deviation Ra. With the arithmetic mean deviation value being less than or equal to 6 pm, any decoration deposited on the textured surface will be sharp.

[0019] In some embodiments, the number of RPc peaks is less than or equal to 60.

[0020] In some embodiments, the arithmetic mean deviation Ra is greater than or equal to 2 pm, preferably greater than or equal to 3 pm.

[0021] In some embodiments, the textured area has a blur greater than or equal to 10% and less than or equal to 80%.

[0022] Blur, also called haze, is defined and measured according to the ISO 14782:1999 standard.

[0023] In some embodiments, the textured area has an AE* color deviation of less than or equal to 3, the color of the textured area being measured on a white background and on a black background.

[0024] The AE* color difference is calculated according to the following equation.

[0025] [Math 1] AE* = VC^ - L^ + C^ - a^+C^ - h*) 2

[0026] The coordinates Li*, L2*, ai*, a2*, bi* and b2* are the colorimetric reflection coordinates in the CIELAB 1976 space measured under a D65 / 10 illuminant. The subscript 1 represents the coordinates on a white background, the subscript 2 represents the coordinates on a black background

[0027] The AE* color difference is a parameter used to measure the opacity of the glass-ceramic substrate. The lower the AE* black / white color difference value, the more opaque the glass-ceramic substrate is considered to be.

[0028] In some embodiments, the textured area includes an enamel decoration having an enamel line resolution of less than or equal to 1.6.

[0029] A line of enamel is applied using silkscreen printing. After drying and firing, the boundary between the enameled and unglazed areas is not straight but forms a line with some curvature. The length of this boundary is measured using an optical microscope. The enamel line resolution, denoted by r, is equal to the ratio of the measured length to the theoretical length of the same boundary (an enamel line with perfectly straight edges).

[0030] In some embodiments, the glass-ceramic substrate has a thickness greater than or equal to 3.2 mm and less than or equal to 4.5 mm.

[0031] This presentation also relates to a glass-ceramic article comprising a glass-ceramic substrate as defined above.

[0032] By way of non-limiting example, the glass-ceramic article may include a glass-ceramic substrate as defined above and a control panel for the glass-ceramic article.

[0033] This presentation also concerns a manufacturing process for a glass-ceramic substrate as defined above, the manufacturing process comprising the following steps: - ceramization of a glass substrate to obtain the glass-ceramic substrate; - chemical treatment of an area to be textured on the glass-ceramic substrate to obtain the textured area.

[0034] The chemical treatment results in a relatively uniform texture of the textured area. The textured area is therefore essentially isotropic.

[0035] Chemical treatment makes it possible to treat large areas of the glass-ceramic substrate, or even the entire main surface of the glass-ceramic substrate.

[0036] In some embodiments, the chemical treatment is carried out at a temperature greater than or equal to 30°C and less than or equal to 60°C.

[0037] In some embodiments, the chemical treatment is carried out for a duration greater than or equal to 100 seconds and less than or equal to 1000 seconds.

[0038] In some embodiments, the glass substrate comprises, by mass percentage, 58-75% silica, 16-25% alumina, 2-4.5% lithium oxide, 0-2% sodium oxide, 0-2% potassium oxide, 0-4% calcium oxide, 0-5% magnesium oxide, 0-5% oxide of barium, 0-5% zinc oxide, 0-5% strontium oxide, 1-6% titanium oxide, 0-3% zirconium oxide, 0-6% phosphorus pentoxide, 0-2% boron oxide, 0-2% iron oxide, 0-2% chromium oxide, 0-2% cobalt oxide, 0-2% refiner, 0-2% colorant.

[0039] By way of non-limiting examples, the refiner may include tin oxide and / or arsenic oxide and / or antimony oxide.

[0040] By way of non-limiting examples, the colorant may include vanadium oxide and / or chromium oxide and / or iron oxide and / or cobalt oxide.

[0041] In some embodiments, the chemical treatment is carried out with an aqueous solution comprising hydrofluoric acid, ammonium fluoride and fluorosilicic acid.

[0042] The mixture allows for the creation of a textured area.

[0043] In some embodiments, the area to be textured of the glass-ceramic substrate, before the chemical treatment step, undergoes a mechanical surface treatment by sandblasting.

[0044] The mechanical surface treatment step by sandblasting makes it possible to texture the area to be textured and to reduce the chemical treatment time of the area to be textured.

[0045] In some embodiments, the chemical treatment is carried out with an aqueous solution comprising hydrofluoric acid.

[0046] In some embodiments, an enamel decoration is applied to the textured area, for example by screen printing.

[0047] This step is carried out after the chemical treatment step. Brief description of the drawings

[0048] Other features and advantages of the object of this presentation will emerge from the following description of embodiments, given by way of non-limiting examples, with reference to the attached figures.

[0049] [Fig. 1] Figure 1 is a schematic perspective view of a glass-ceramic article according to one embodiment.

[0050] [Fig. 2] Figure 2 is a schematic cross-sectional view of a textured area according to one embodiment.

[0051] [Fig. 3] Figure 3 is a flowchart representing the steps of a manufacturing process according to an embodiment.

[0052] Across all figures, common elements are identified by identical numerical references. Detailed description

[0053] Figure 1 is a schematic longitudinal cross-sectional view of a glass-ceramic article 10 according to one embodiment.

[0054] In the embodiment of Figure 1, the glass-ceramic article 10 comprises a glass-ceramic substrate 12 and a control panel 14 for the glass-ceramic article. The glass-ceramic article 10 may comprise only the glass-ceramic substrate 12, i.e., the glass-ceramic article may be devoid of a control panel.

[0055] In the embodiment of Figure 1, the glass-ceramic substrate 12 comprises a main surface 16 which includes a textured area 18. The main surface 16 of the glass-ceramic substrate 12 may include several textured areas 18. The main surface 16 of the glass-ceramic substrate 12 may include a single textured area 18 whose surface is identical to the surface of the glass-ceramic substrate 12. The glass-ceramic substrate 12 has a thickness E.

[0056] In the embodiment of Figure 1, the textured area 18 includes an enamel decoration 20. The textured area 18 can include several enamel decorations 20.

[0057] Figure 2 is a schematic cross-sectional view of textured area 18 of Figure 1.

[0058] Figure 3 is a flowchart representing the steps of a manufacturing process 100 of the glass-ceramic substrate 12.

[0059] The manufacturing process 100 includes a ceramicization step 102 of a glass substrate to obtain the glass-ceramic substrate 12 and the chemical treatment 104 of a texturizing area of ​​the glass-ceramic substrate 12 to obtain the textured area 18.

[0060] In some embodiments, the chemical treatment step 104 is preceded by a mechanical surface treatment step 106 carried out by sandblasting.

[0061] The manufacturing process 100 may also include a step of depositing enamel decoration 20 108 onto the textured area 18, for example by screen printing.

[0062] Examples 1 to 3 (Ex1 to Ex3)

[0063] Examples 1 to 3 are performed on glass-ceramic substrates where the textured area is obtained by chemically treating the area to be textured. The aqueous chemical treatment solution comprises hydrofluoric acid (HF), ammonium fluoride (NEUF), and fluorosilicic acid (FhSiFe). The composition of the solution, along with the temperature and duration of the chemical treatment, is given in Table 1 below.

[0064] Examples 4 to 8 (Ex4 to Ex8)

[0065] Examples 4 to 8 are carried out on glass-ceramic substrates where the textured area is obtained by mechanical surface treatment followed by chemical treatment of the area to be textured.

[0066] The mechanical surface treatment is performed by sandblasting. The abrasive consists of 120 mesh garnet particles. The particles are projected onto the area to be textured by nozzles at a pressure between 2 and 5 bar. The feed pitch is between 6 and 36 mm, and the vertical movement speed of the nozzles is between 250 and 500 mm / s. The area to be textured is treated in a single pass.

[0067] The aqueous chemical treatment solution contains hydrofluoric acid (HF). The composition of the solution is given in Table 1 below, along with the duration of the chemical treatment expressed as relative time.

[0068] Table 1 includes the chemical treatment data for examples 1 to 8, as well as the values ​​of thickness E (in mm), RPc, Ra (pm), blur (in %), AE* and line resolution r for examples 1 to 8.

[0069] The values ​​of the different roughness parameters, Ra and Rpc, were measured using a Mitutoyo SJ401 mechanical probe and evaluated according to ISO 4287:2010 over an evaluation length of 4 mm to 12.5 mm and equipped with a stylus of type "12AAC731".

[0070] The AE* values ​​are measured using a Byk Gardner 45 / 0 gloss spectro-guide.

[0071] The chemical treatment data includes the hydrofluoric acid concentration (in M), the NH4F and HF concentrations (in g / L), and the H2SiFe concentration (in mol / L). The temperature T (in °C) of the chemical treatment bath is also included. is between 30°C and 60°C and the time t (in relative time) of chemical treatment is between 50 seconds and 1200 seconds.

[0072] [Table 1]

[0073] We observe that the mechanical surface treatment step by sandblasting reduces chemical treatment time while producing a textured area with good blur and AE* values. Furthermore, the line resolution values ​​r allow for the application of enamel decorations of acceptable visual quality on the textured area.

[0074] Comparative examples 1 to 4 (ExC1 to ExC4)

[0075] Comparative examples 1 to 4 are produced on glass-ceramic substrates processed in a rolling mill using a known method. The rolling mill rollers are themselves textured to imprint a pattern onto the laminated glass material.

[0076] Table 2 lists the values ​​for thickness E (in mm), RPc, and Ra (pm), blur (%), AE* and line resolution r for comparative examples 1 to 4

[0077] [Table 2]

[0078] Although the present description has been made with reference to a specific embodiment, it is evident that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, individual features of the various embodiments mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered illustrative rather than restrictive.

Claims

DEMANDS

1. Vitre-ceramic substrate (12) for cooking device, comprising a main surface (16) intended to receive cooking elements by direct contact, the main surface (16) having a textured zone (18), the textured zone (18) having a number of peaks RPc less than or equal to 115 and an arithmetic mean deviation Ra greater than or equal to 1 pm and less than or equal to 6 pm.

2. Glass-ceramic substrate (12) according to claim 1, wherein the textured area (18) has a blur greater than or equal to 10% and less than or equal to 80%.

3. Glass-ceramic substrate (12) according to claim 1 or 2, wherein the textured area (18) has a color deviation AE* less than or equal to 3, the color of the textured area (18) being measured on a white background and on a black background.

4. Vitreous ceramic substrate (12) according to any one of claims 1 to 3, the textured area (18) comprises an enamelled decoration (20) having an enamelled line resolution less than or equal to 1.

6.

5. Glass-ceramic substrate (12) according to any one of claims 1 to 4, having a thickness (E) greater than or equal to 3.2 mm and less than or equal to 4.5 mm.

6. Glass-ceramic article (10) comprising a glass-ceramic substrate (12) according to any one of claims 1 to 5.

7. A method for manufacturing (100) a glass-ceramic substrate (12) according to any one of claims 1 to 5, comprising the following steps: - ceramization (102) of a glass substrate to obtain the glass-ceramic substrate (12); - chemical treatment (104) of a texturizing area of ​​the glass-ceramic substrate (12) to obtain the textured area (18).

8. Manufacturing process (100) according to claim 7, the chemical treatment (104) is carried out with a solution comprising hydrofluoric acid, ammonium fluoride and fluorosilicic acid.

9. A manufacturing method (100) according to claim 7, wherein the area to be textured of the glass-ceramic substrate (12), prior to the chemical treatment step (104), undergoes a mechanical surface treatment (106) by sandblasting.

10. A manufacturing method (100) according to claim 9, wherein the chemical treatment (104) is carried out with a solution comprising hydrofluoric acid.

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