VITROCERAMIC SUBSTRATE FOR COOKING DEVICES, VITROCERAMIC ARTICLE AND MANUFACTURING METHOD

Abstract

A glass-ceramic substrate (12) for a 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 µm and less than or equal to 6 µm. A glass-ceramic article (10) comprising such a glass-ceramic substrate (12) and a method for manufacturing such a glass-ceramic substrate. Figure for the abstract: Fig. 1

Description

Title of the invention: VITRO-CERAMIC SUBSTRATE FOR COOKING DEVICE, VITRO-CERAMIC ARTICLE AND MANUFACTURING METHOD technical field

[0001] The present disclosure relates to a glass-ceramic substrate for a cooking device. The present disclosure also relates to a method for manufacturing such a substrate. Prior art

[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 ceramicizing heat treatment or for glass-ceramics after ceramicizing heat treatment of glass.

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

[0005] In order 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 by direct contact cooking elements, such as pans and / or pots.

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

[0007] Also, there is a need for a glass-ceramic substrate that is easy to manufacture and has a transparency that allows the user to see the indicator lights without making the electronic components visible. Description of the invention

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

[0009] To this end, the present description relates to 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 zone, the zone textured exhibiting a peak number 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 this does not refer to a glass-ceramic substrate with a coating deposited on it. Therefore, the textured area is not a coating deposited on the substrate but rather an area obtained following a treatment of the substrate itself. Consequently, there is no risk of delamination between the glass-ceramic substrate and a coating that may have been deposited on 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 comprising the glass-ceramic substrate. However, the textured area may include decorative elements deposited on it, for example, layers of enamel printed by 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 may 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, that is to say that the variation in the measurement of the number of peaks RPc varies little according to the direction of measurement.

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

[0017] A number of RPc peaks less than or equal to 115 makes it possible to obtain a glass-ceramic substrate which reduces the visibility of the electronic components of a glass-ceramic article comprising the glass-ceramic substrate.

[0018] The scratch-resistant properties of the glass-ceramic substrate improve with the value of the arithmetic mean deviation Ra. With the value of the arithmetic mean deviation 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 certain 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 ISO 14782:1999.

[0023] In certain embodiments, the textured area has an AE* color difference 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 color difference AE* is calculated according to the following equation.

[0025] [Math.l] * F~ 7~ 72 “ ~T AE = +(«2'^1 / + (¼

[0026] The coordinates Li*, L2*, ai*, a2*, bi* and b2* are the colorimetric reflection coordinates in the CIELAB 1976 color 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] An enamel line is deposited by screen printing. After drying and firing the enamel, the boundary between the enameled and unenameled areas is not straight but forms a line with a certain degree of curvature. The length of the boundary between the enameled and unenameled areas is measured using an optical microscope. The enamel line resolution, identified by r, is equal to the ratio between the measured length and the theoretical length of this 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] The present disclosure 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] The present description also relates to a method for manufacturing a glass-ceramic substrate as defined above, the manufacturing method 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 makes it possible to obtain a relatively uniform texturing of the textured area. The textured area is therefore substantially 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 certain 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% barium oxide, 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% fining agent, 0-2% coloring.

[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 texturing of the 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 deposited on 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 subject matter of this presentation will become apparent from the following description of embodiments, given by way of non-limiting examples, with reference to the attached figures.

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

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

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

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

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

[0054] In the embodiment of [Fig. 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 is notably free of a control panel.

[0055] In the embodiment of [Fig. 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 [Fig.1], the textured area 18 includes an enamel decoration 20. The textured area 18 can include several enamel decorations 20.

[0057] [Fig.2] is a schematic cross-sectional view of textured area 18 of [Fig.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 textured 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 108 of enamelled decoration 20 on the textured area 18, for example by screen printing.

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

[0063] Examples 1 to 3 are carried out on glass-ceramic substrates in which the textured area is obtained by chemical treatment of the area to be textured. The aqueous chemical treatment solution comprises hydrofluoric acid (HF), ammonium fluoride (NH4F), and fluorosilicic acid (H2SiF6). The composition of the solution, as well as the temperature and duration of the chemical treatment, are 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 whose textured area is obtained by mechanical surface treatment followed by chemical treatment of the area to be textured.

[0066] The mechanical surface treatment is carried out 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 comprises hydrofluoric acid (HF). The composition of the solution is given in Table 1 below, along with the duration of the chemical treatment expressed in 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 45 / 0 gloss Byk Gardner spectro-guide.

[0071] The chemical treatment data include the hydrofluoric acid concentration (in M), the NH4F, HF concentration (in g / L), and the H2SiF6 concentration (in mol / L). The temperature T (in °C) of the chemical treatment bath is between 30°C and 60°C, and the chemical treatment time t (in relative time) is between 50 seconds and 1200 seconds.

[0072] [Tables 1] Exl Ex2 Ex3 Ex4 Ex5 Ex6 Ex7 Ex8 E 3.94 3.94 3.94 3.53 3.66 3.67 3.73 3.92 HF 9.4 22 9.4 14.3 14.2 13.9 14.5 13.9 nh4f, h F 500 500 500 H2SiF6 0.1 0.1 0.1 time 7.5t 5t 5t It 2.5t 4t 5.5t 7.5t RPc 69.97 51.93 110.06 36.11 25.23 20.90 18.21 19.53 Ra 1.63 2.89 1.49 4.88 5.53 4.81 5.16 5.05 Blur 69.81 70.89 66.53 72.59 49.36 31.26 18.16 13.24 AE* 0.51 0.48 0.59 0.57 0.65 1.2 1.95 2.26 r 1.57 1.43 1.38 1.3 1.3

[0073] It is observed 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 visually acceptable quality enamel decorations onto the textured area.

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

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

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

[0077] [Tables2] ExCl ExC2 ExC3 ExC4 E 3.98 3.54 3.41 3.29 RPc 80.04 80.50 88.10 83.73 Ra 0.16 0.16 0.14 0.13 Blur 7.50 4.74 3.35 2.71 AE* 1.83 3.02 3.34 3.90 r 1.2 1.2 1.2 1.2

[0078] Although the present exposition has been described 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 ways of Additional details. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

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

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

Images