Glass-ceramic article

Abstract

The present invention relates to a glass-ceramic article comprising at least one substrate, such as a plate, made from a glass-ceramic, the substrate having a microtextured surface with an arithmetic mean surface roughness Ra of 0.14 to 0.40 μm, measured according to standard ISO 4287, and preferably a maximum cross-sectional height Rt of 1.15 to 5.00 μm, measured according to standard ISO 4287. The invention has therefore made it possible to develop a glass-ceramic product whose top surface hides glass defects that may occur during the manufacturing process, and in which scratches cause only very low variations in brightness, thereby simultaneously satisfying several constraints.

Description

Technical Field

[0001] The present invention relates to the field of glass ceramics. More particularly, the present invention relates to articles or products made of glass ceramics, and in particular to glass ceramic plates intended to be used as furniture surfaces and / or cooking surfaces. By glass ceramic or glass ceramic article, the inventors intend an article based on a substrate (such as a plate) made of a glass ceramic material, which substrate can be provided with decorative or functional accessories or additional elements required for its final purpose, and the article can refer to the substrate alone or even one provided with additional elements (for example, a cooking plate provided with a control panel, a heating element, etc.).

Background Art

[0002] Conventionally, glass ceramic plates have been used as cooking plates or can also be combined with heating elements for other applications, for example, to form inserts for fireplaces. Recently, their use has been extended to other areas of daily life, and glass ceramic plates can be used to form furniture surfaces, particularly for cooking countertops, central islands, consoles, etc. The area of the surface occupied by glass ceramics in these new applications is larger than before.

[0003] Glass ceramic is originally a glass called precursor glass or mother glass or green glass, and due to its special chemical composition, controlled crystallization can be induced by an appropriate heat treatment called ceramization. This special partially crystallized structure imparts unique properties to the glass ceramic.

[0004] At present, there are various types of glass-ceramic plates, and considering that it is very difficult to make modifications to these plates and / or the processes used to obtain them without generating a risk of having an adverse effect on the desired properties, each of the different types is the result of a great deal of research and many trials. In particular, for the purpose of being used as a hob top surface, the glass-ceramic plate generally needs to be low enough to at least partially conceal the heating element that is below when the switch is off, and high enough for the user to be able to see whether the switch of the heating element is on or not depending on the situation (such as radiant heating) for safety reasons, having a transmittance in the visible light wavelength range. The glass-ceramic plate also needs to have a high transmittance at wavelengths in the infrared range, especially in the case of a radiant heater, and it is also necessary to make the display of the control panel for giving the power level of the heating zone and the indication regarding the operation of the hob top surface visible, as well as the indicator lights. The glass-ceramic plate also needs to have sufficient mechanical strength required in the field of use. In particular, when it is to be used as a cooking plate in the field of household appliances or as a furniture surface, the glass-ceramic plate needs to have good resistance to pressure, impact (such as support and dropping of the appliance), etc.

[0005] The most common glass-ceramic cooking plates are dark in color, especially black or brown or orange-brown. However, there are also plates made of a transparent substrate with an opacifier on the lower side, and in particular, plates that are milky white or white opaque.

[0006] There is a glass-ceramic plate commercially available under the trade name Kerablack+ from Eurokera. This has a roughness of about 0.1 μm Ra and 1.0 μm Rt.

[0007] The roughness Ra is a known roughness parameter, which is the arithmetic mean roughness of the cross-sectional curve defined over the entire evaluation length (the arithmetic mean of the absolute values of the deviations between consecutive peaks and valleys), and the roughness Rt is the total height of the deepest valley and the highest peak of the cross-sectional curve over the entire evaluation length. The roughness Ra and roughness Rt considered in this specification are measured over an evaluation length of 4 mm using a probe with the reference number SJ401 manufactured by Mitutoyo Corporation in accordance with the standard ISO4287.

[0008] Also, a black polished glass ceramic plate (Kanger (registered trademark)) with a surface roughness of Ra = 0.03 μm and Rt = 0.4 μm is commercially available. The wear of the surface that is inevitable during use due to cleaning with a polishing sponge and the movement of the cooking container does not affect the gloss of this glass ceramic. However, polishing means an additional process in the manufacturing method that should be avoided due to cost and complexity of execution.

[0009] Also, a glass ceramic plate (unpolished Kanger (registered trademark)) with a surface roughness of Ra = 0.8 μm and Rt = 6.3 μm and a highly textured upper surface is commercially available. These plates have major drawbacks. The gloss varies greatly due to surface wear.

[0010] In addition, such a strong texture makes it difficult to clean the surface because it is difficult to remove food residues caught in the valleys of the surface.

[0011] From Japanese Patent Application Laid-Open No. 2009-149468, a glass-ceramic plate with an Ra of 0.04 to 0.13 μm is known for the purpose of avoiding glare caused by reflection of kitchen lighting while maintaining the gloss level of the cooking surface. To obtain this level of roughness, a complex method is described that requires blasting at least one of the rotating rolls with alumina powder consisting of grains with an average diameter of 550 μm and then polishing it. The roughness cross-sectional curve obtained on the glass-ceramic substrate has a specific shape in this case, where the valleys are flat and the peaks are curved surfaces. This delicate and complex method will significantly increase the manufacturing cost of the glass-ceramic plate.

[0012] Furthermore, with this low surface roughness having this specific cross-sectional curve presenting a very low Rt, defects that may occur in the process of the manufacturing method implemented in two main stages of forming a flat glass ribbon by roll processing between rollers and subsequently converting the flat glass to glass-ceramic cannot be sufficiently hidden.

Summary of the Invention

Problems to be Solved by the Invention

[0013] The present invention thus seeks to develop an improved glass-ceramic product that limits the visibility of defects that may occur during the manufacturing process while maintaining the acceptable wear resistance of the surface. Defects in the flat glass obtained by roll processing can be bubbles, pits, stones (grains of raw materials that did not melt), crystallization pieces, or "patches" originating from deposits on the roll processing rolls. Defects that occur during the processing and use of the cooking surface can be scattered scratches, wear areas caused by rubbing cooking utensils (a series of scratches) or rubbing with a sponge, and furthermore, stains.

[0014] In particular, the present invention aims at a novel glass-ceramic plate intended to be used together with one or more heating elements such as a cooking plate or to be used as a furniture surface, and these plates maintain an acceptable abrasion resistance without harming other properties required for their use, in particular without harming ease of maintenance and cleaning, resistance, in particular mechanical resistance, and without being disadvantageous to their lifespan, while at the same time allowing for the presence of decoration or additional functions if necessary, and is also considered to propose a simple and, if possible, flexible solution.

[0015] This object is achieved by imparting a specific microtexture to the upper surface of the glass-ceramic product developed according to the present invention.

Means for Solving the Problems

[0016] The present invention thus relates to a novel glass-ceramic article comprising at least one substrate such as a plate made of glass-ceramic, said substrate having a surface with a microtexture such that the arithmetic mean surface roughness Ra measured according to ISO 4287 is 0.14 to 0.40 μm, preferably 0.15 to 0.30 μm, and the maximum cross-sectional height (total roughness) Rt measured according to ISO 4287 is 1.15 to 5.00 μm, preferably 1.25 to 3.00 μm.

[0017] The surface with the microtexture is intended to form, in particular, the upper surface of the glass-ceramic article, i.e., the surface facing the user.

[0018] Advantageously, the substrate is based on a glass-ceramic that is 3 to 6 mm and has a dark appearance or is black transparent, with a light transmittance TL of less than 20%, preferably less than 10% under light source D65, and an optical transmittance of less than 30%, preferably less than 20%, more preferably less than 15% at a wavelength of 625 nm (the optical properties are measured at this wavelength characteristic of the emission of a red display).

[0019] The optical transmittance is determined by a known method by taking the ratio of the transmitted intensity to the incident intensity at any wavelength.

[0020] The term "intrinsic" is understood to mean that the substrate has such transmission characteristics alone, in the absence of any coating.

[0021] Optical measurements are carried out in accordance with standard EN410. In particular, the visual transmittance TL is measured at 2° using a light source D65 in accordance with standard EN410, and is the total transmittance taking into account both the direct transmittance and any possible diffuse transmittance (in particular, integrated over the entire visible domain and weighted by the spectral sensitivity curve of the human eye), and the measurement is carried out using, for example, a spectrophotometer equipped with an integrating sphere (in particular, a spectrophotometer sold as product Lambda 950 by Perkin Elmer).

[0022] However, the present invention can also be applied to light-colored glass-ceramic plates, in particular milky white or white opaque plates.

[0023] Other parameters such as Ssk, Sp, and Sv are also used to identify the roughness profile.

[0024] Ssk is the skewness with respect to the mean plane. Ssk < 0 indicates that the height distribution is asymmetric below the mean plane (there are many valleys on the surface). Ssk > 0 indicates that the height distribution is asymmetric above the mean plane (there are many peaks on the surface).

[0025] Sp represents the maximum height of the peaks.

[0026] Sv is the maximum depth of the valleys.

[0027] According to the present invention, the microtexture preferably has a skewness Ssk of -0.20 to -1.1 μm, preferably -0.3 to -1 μm, and a maximum peak height Sp of 0.7 to 10.0 μm, preferably 0.8 to 5.0 μm. In particular, the maximum valley depth Sv of the microtexture is 0.7 to 10.0 μm, preferably 0.8 to 5.0 μm.

[0028] Generally, on the lower side of the article according to the present invention, there are ellipsoidal teardrops with a height of 60 to 120 μm, preferably 80 to 100 μm. In particular, the teardrop-shaped parts have an interval of 250 to 500 μm, preferably 300 to 400 μm in the vertical direction when measured between the edges.

[0029] Another object of the present invention is a method for manufacturing the glass-ceramic article described above by roll-treating mother glass between two rollers, one of which is a roller that has been shot-peened with a particulate material having a Vickers hardness HV1 of 3 to 10 GPa, preferably 4 to 8 GPa. The mother glass thus roll-treated is subsequently subjected to a conventional ceramization process.

[0030] Advantageously, the shot peening treatment is carried out using particles with an average diameter of 0.2 to 2 mm, preferably 0.5 to 1.2 mm. These particles may be, for example, martensitic steel particles. The shot peening is advantageously air injection type shot peening at a pressure of preferably 2 to 6 bar, or even 3 to 5 bar. The particles are typically fired at a speed of 1 to 5 kg / min, or even 2 to 4 kg / min, preferably in a direction perpendicular to the roller surface. The coverage rate of the shot peening is advantageously 90 to 110%, preferably about 100%, that is, the roller surface is completely peened. The roller thus peened is preferably used in the method according to the invention without polishing. The peened roller typically has a roughness Ra of 0.6 to 1.2 μm, or even 0.8 to 1.0 μm, and preferably a roughness Rt of more than 4 μm, preferably more than 8 μm.

[0031] For the sake of confirmation, the production of glass-ceramic plates is generally carried out as follows: Glass of a composition selected to form a glass-ceramic is melted in a melting furnace, and the molten glass is then roll-processed by passing the molten glass between rotating rolls to form a standard ribbon or sheet, and this glass ribbon is cut to the desired dimensions. The plate thus cut is decorated with an enamel-based decoration deposited by screen printing or enamel jet, and subsequently itself is ceramized by a method known per se, which ceramization consists of firing the plate according to a selected thermal profile to convert the glass into a polycrystalline material called "glass-ceramic" having a coefficient of thermal expansion of zero or almost zero and in particular resistant to thermal shock up to 700 °C. The ceramization generally includes a step of gradually raising the temperature to the nucleation stage (e.g., 650 to 830 °C) with a variable duration of 5 to 90 minutes, a new temperature increase for growing the crystals (e.g., within the range of 850 to 1100 °C in the case of a milky white / opaque glass-ceramic), maintaining the temperature for the crystal growth stage for several minutes (e.g., 5 to 30 minutes), and then rapid cooling to room temperature.

[0032] When applicable, this process also includes cutting operations (generally before ceramization) using, for example, water jets, mechanical scoring using a scoring wheel, etc., and subsequent shaping operations (grinding, chamfering, etc.).

[0033] The substrate (or, if formed only of the substrate, the article itself according to the invention) is generally in the form of a plate, in particular a plate for use with at least one light source and / or heating element, in particular for covering or receiving these, or for use as a furniture surface. This substrate (or each such plate) generally has a geometric shape, in particular rectangular, or even square, or even circular, or elliptical, etc., and generally has one face (or visible face or external face, generally the upper face in the position of use) facing the user in the position of use, another face (or internal face, generally the lower face in the position of use), which is generally hidden, for example, in a furniture frame or casing in the position of use, and an edge (or thickness). The upper or external face is generally flat, but locally may have at least one raised area and / or at least one recessed area and / or at least one opening and / or a chamfered edge, and these shape variations in particular constitute a continuous variation of the plate. The lower or internal face may also be flat and smooth, or may be provided with drip-shaped portions.

[0034] The substrate may be based on any glass ceramic, and this substrate advantageously has a coefficient of thermal expansion (CTE) of zero to almost zero, in particular, the coefficient of thermal expansion is less than (in absolute value) 30×10 -7 K -1 between 20 and 700 °C, and in particular less than 15×10 -7 K -1 between 20 and 700 °C, or even less than 5×10 -7 K -1 between 20 and 700 °C.

[0035] In particular, by using a black or brown substrate, in combination with a light source arranged below, a light-emitting zone or a decoration can be displayed, and at the same time any elements below are hidden. It may be based on a black glass ceramic containing crystals having a β-crystal structure in the residual glass phase, and the absolute value of its coefficient of thermal expansion is preferably 15×10 -7 K -1 or less, or even 5×10 -7 K -1 or less, such as the glass ceramic of the plate commercially available under the trade name Kerablack+ from Eurokera.

[0036] The substrate according to the invention may, if desired, be coated with a normal enamel design, or, if desired, be coated with an opaque paint layer on a part of the lower side of the substrate.

[0037] The article according to the invention may further comprise, associated with or combined with the substrate, one or more light sources and / or one or more heating elements (one or more radiant or halogen elements, and / or one or more atmospheric gas burners, and / or one or more induction heating means, etc.). One or more light sources may be integrated or combined with one or more display unit structures, an electronic control panel by touch sensor control, and a digital screen, etc. These light sources are preferably formed by a display consisting of a plurality of light-emitting diodes arranged at a certain interval, and the diodes may, if desired, be accompanied by one or more waveguides.

[0038] In particular, the article according to the invention has good heat resistance suitable for the use of various types of heaters and does not cause problems of maintenance, scratches, or wear as shown hitherto.

[0039] The following examples illustrate the invention without limitation, with reference to the drawings.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0041] For the production of the glass-ceramic plate according to the present invention, the surface of the upper roll treatment roller is modified as follows.

[0042] Air injection shot peening is performed by blasting shots made of steel (martensite) containing particles with a particle size of 0.5 to 1.2 mm at a right angle to the surface of the mirror-polished roller. The blasting pressure is about 4 bar. The blasting speed of the shots is approximately 3 kg / min. After 4 passes, the present inventors ensure the formation of a surface state having a roughness Ra of 0.8 to 1 μm and a gloss corresponding to an Rt higher than 8 μm (satiny) on the roller surface.

[0043] When the shot peening is completed, the roller is cleaned with alcohol.

[0044] The present inventors thus obtain a specific random texture on the roller surface.

[0045] The lower roller is prepared to form protrusions.

[0046] Using the roller prepared in this way, the mother glass is continuously roll-processed for several tens of hours (the "roll-processing cycle"), during which the ribbon of the mother glass is continuously passed between two rollers. After this roll-processing cycle, the upper roller is subjected to a continuous polishing process until a mirror-polished surface is obtained, and then, as described above, texture can be imparted to the roller again by shot peening.

[0047] Examples according to the present invention are samples of roll-processed glass taken at different times during the same roll-processing cycle.

Example

[0048] Example 1 Samples of the textured mother glass of Example 1 are taken after 1 hour of operation of the roll-processing roller.

[0049] Example 2 Samples of the textured mother glass of Example 2 are taken at a time t1 corresponding to the operation time of the roll-processing roller for several tens of hours.

[0050] Example 3 Samples of the textured stock glass from Example 3 are taken at the time t2 of the roll-processing roller operation (equal to approximately twice t1).

[0051] The roughness measurement values Ra and Rt are measured at 15 points over an evaluation length of 4 mm using a Mitutoyo Sj-400 roughness meter on a 594×525 mm plate in accordance with the standard ISO4287. The finish of the surface property evaluation is by an optical interference method that gives the parameters Ssk, Sp, and Sv established in accordance with the standard ISO25178. All these characteristic values are shown in Table 1.

[0052] Three examples according to the present invention were compared with three commercially available products constituting the comparative examples: Eurokera KB+ (Comparative Example 1), Kanger (registered trademark) unpolished product (Comparative Example 2), and Kanger (registered trademark) polished product (Comparative Example 3).

Table 1

[0053] The glass ceramic sample is subjected to a wear test representing kitchen use as defined below.

[0054] The gloss difference is measured as follows.

[0055] The gloss difference is the difference between the gloss of the worn area and the gloss of the non-worn area divided by the gloss of the non-worn area. The larger the absolute value of this difference, the greater the contrast between the worn area and the non-worn area.

[0056] The worn area is prepared using a 18 mm diameter disk obtained from Norton silicon carbide (SiC) P240 grit abrasive paper. The disk is mounted on a Taber Linear Abraser device, and a pressure of 5 N / cm2 is applied to the SiC disk. The reciprocating motion (1 cycle) is performed at a speed of 15 cycles / min with a stroke of 38.1 mm. Three worn areas are created on the sample to be characterized.

[0057] The gloss is measured using a device of the Color i7 type sold by X-Rite.

[0058] For each of the three worn areas, three measurements are taken: once at the center and twice on both sides of the initial position. The gloss value of the worn sample is the average gloss of the three worn areas.

[0059] On the non-worn sample, nine measurements are also taken and averaged to obtain the gloss value of the non-worn area. The gloss difference is reported together with the standard deviation with respect to the average of the gloss differences.

[0060] The results are reported in Table 2.

[0061] Table 2 also -0.8 μm from the maximum of the height distributionThe characteristics of these zones are also shown, i.e., the percentage of the surface occupied by these zones (dist0.8), the average area of these zones, and the density of these zones (see Images 1 - 4).

[0062] These characteristics are established through image processing performed on the images obtained by the optical interference method.

[0063] Located at a depth of -0.8 μm with respect to the maximum of the height distribution The regions are shown in white in Figures 1 - 4. [Table 2]

[0064] As can be seen from Table 1, the peak height value and the valley depth value are significantly larger for the examples according to the present invention than for Comparative Example 1 (Eurokera KB+). The skewness Ssk is not significantly different from Comparative Example 1 at the start of the roll - processing cycle, but decreases significantly during the roll - processing cycle (Examples 2 and 3 according to the present invention).

[0065] As can be seen from Table 2, the percentage of the surface occupied by the valleys of the image established by the optical interference method (the percentage of the surface occupied by the region located at a depth of 0.8 μm with respect to the maximum height distribution (Sp)) is much larger for the examples according to the present invention than for Comparative Example 1. The area and further the density of the valleys on the surface of the glass - ceramic according to the examples of the present invention are significantly larger compared to Comparative Example 1. The valleys are perceivable to the naked eye as bright spots on the surface under standard observation conditions (observing the plate at an inclination of 45°, a distance of 60 cm, and an illuminance of about 2000 Lux).

[0066] These characteristics are important for explaining the reduced perception of defects. The higher density of valleys on the surface of the glass - ceramic according to the present invention modifies the perception of the defects present on the surface of the glass - ceramic that can occur during the plate - manufacturing process under the above - described observation conditions.

[0067] As a non-limiting example, defects with low perception on the surface of the article according to the present invention as compared to the surface of Comparative Example 1 may be bubbles with a diameter of less than 0.8 mm, scattered scratches with a length of less than 50 mm, and spots with a diameter of less than 1 mm.

[0068] As shown by the straight line plotted in FIG. 5, it can be seen that the gloss difference (values in Table 2) correlates with the parameter Ssk (values in Table 1) in the three Comparative Examples and the three Examples according to the present invention. R 2 The value is close to 1.

[0069] The gloss difference (in absolute value) obtained with the glass-ceramic according to the present invention is slightly higher than that of the glass-ceramic corresponding to Comparative Example 1 (Eurokera KB+), but is maintained significantly lower than that observed with the glass-ceramic corresponding to Comparative Example 2 (Kanger (registered trademark) unpolished), which is considered unacceptable. The gloss difference (in absolute value) is larger than that observed with the glass-ceramic corresponding to Comparative Example 3 (polished Kanger (registered trademark)), but the production of this glass-ceramic requires an additional polishing step as compared to the glass-ceramic according to the examples of the present invention, which should be avoided due to the additional cost and the complexity of implementing this step.

[0070] The texture profile according to the present invention can achieve a compromise point that satisfies both the need to hide defects that may occur during the process of the plate manufacturing method and the need to limit the gloss difference between the worn area and the non-worn area.

[0071] The texture profile according to the present invention is particularly suitable for black or dark glass-ceramic plates, but is also advantageously applicable to milky white, light-colored, or transparent white glass-ceramic plates as long as they can modify the out-of-plane appearance.

[0072] The present invention thus enables the development of a glass-ceramic product that, in a simple and economical way, hides glass defects that may occur during the manufacturing process on its upper surface and has only very slight variations in gloss caused by wear. On the other hand, it also takes into account the specific, particularly thermal and mechanical constraints in the use of the above product and maintains a durable and easily cleanable glass-ceramic product.

[0073] The article according to the present invention can be advantageously used, in particular, in the manufacture of a new series of cooking plates or range tops for stoves, or a new series of kitchen countertops, consoles, cupboards, island-type central units, or inserts for fireplaces. The present disclosure includes the following aspects of the invention: <Claim 1> A glass-ceramic article comprising at least one substrate made of glass-ceramic, for example a plate, wherein the substrate has a surface with a microtexture such that the arithmetic mean surface roughness Ra measured according to standard ISO 4287 is 0.14 to 0.40 μm, preferably 0.15 to 0.30 μm. A glass-ceramic article. <Aspect 2> The glass-ceramic article according to Aspect 1, characterized in that the maximum cross-sectional height Rt measured according to standard ISO 4287 is 1.15 to 5.00 μm, preferably 1.25 to 3.00 μm. <Aspect 3> The glass-ceramic article according to any one of Aspects 1 and 2, characterized in that the substrate is based on a glass-ceramic that is 3 to 6 mm thick, black and transparent, having an optical transmittance TL of less than 20%, preferably less than 10% under a light source D65, and an optical transmittance of less than 30%, preferably less than 20% for a wavelength of 625 nm. <Aspect 4> The glass-ceramic article according to any one of Aspects 1 to 3, characterized in that the microtexture has a skewness Ssk of -0.2 to -1.1 μm, preferably -0.3 to -1.0 μm. <Aspect 5> The glass-ceramic article according to any one of Aspects 1 to 4, characterized in that the microtexture has a maximum peak height Sp of 0.7 to 10.0 μm, preferably 0.8 to 5.0 μm. <Aspect 6> The glass-ceramic article according to any one of Aspects 1 to 5, characterized in that the microtexture has a maximum valley depth Sv of 0.7 to 10.0 μm, preferably 0.8 to 5.0 μm. <Aspect 7> The glass-ceramic article according to any one of Aspects 1 to 6, characterized in that the proportion of the surface area exceeding 0.8 μm from the maximum in the height distribution is 2 to 8%, preferably 2 to 4%. <Aspect 8> The average area of the valleys is 2×10 -3 mm 2 ~10×10 -3 mm 2 , preferably 3×10 -3 mm 2 ~8×10 -3 mm 2 . The glass-ceramic article according to any one of Aspects 1 to 7, characterized in that it is. <Aspect 9> The glass-ceramic article according to any one of Aspects 1 to 8, characterized in that the lower surface has an elliptical drop-shaped portion with a height of 60 to 120 μm, preferably 80 to 100 μm. <Aspect 10> The glass-ceramic article according to any one of Aspects 1 to 9, characterized in that the drop-shaped portion below the base material has a vertical interval of 250 to 500 μm, preferably 300 to 400 μm, when measured between edges. <Aspect 11> The glass-ceramic article according to any one of Aspects 1 to 10, characterized in that the gloss difference between the worn area and the non-worn area is less than 20% in absolute value, preferably less than 15%. <Aspect 12> A method for manufacturing a glass-ceramic article according to any one of Aspects 1 to 11, comprising roll-treating mother glass between two rollers, wherein one of the two rollers is a roller that has been shot-peened with a particulate material having a Vickers hardness HV1 of 3 to 10 GPa, preferably 4 to 8 GPa, and the mother glass thus roll-treated is subsequently subjected to a ceramization process. <Aspect 13> The method according to Aspect 12, characterized in that the roller that has been shot-peened has a roughness Ra of 0.6 to 1.2 μm, preferably 0.8 to 1 μm. <Aspect 14> The method according to any one of Aspects 12 and 13, characterized in that the roller that has been shot-peened has a roughness Rt of more than 4 μm, preferably more than 8 μm. <Aspect 15> The method according to any one of Aspects 12 to 14, characterized in that the roller that has been shot-peened is not subjected to a polishing process after the shot-peening process.

Claims

1. A glass-ceramic article comprising at least one substrate made of glass-ceramic, for example a plate, wherein the substrate has a surface with a microtexture such that the arithmetic mean surface roughness Ra measured according to ISO 4287 is 0.14 to 0.40 μm, preferably 0.15 to 0.30 μm, and the maximum cross-sectional height Rt measured according to ISO 4287 is 1.15 to 5.00 μm, preferably 1.25 to 3.00 μm, a glass-ceramic article.

2. The glass-ceramic article according to claim 1, characterized in that the substrate is based on a glass-ceramic that is 3 to 6 mm thick, black transparent, has a light transmittance TL of less than 20%, preferably less than 10% under a light source D65, and an optical transmittance of less than 30%, preferably less than 20% for a wavelength of 625 nm.

3. The glass-ceramic article according to any one of claims 1 and 2, characterized in that the microtexture has a skewness Ssk of -0.2 to -1.1 μm, preferably -0.3 to -1.0 μm.

4. The glass-ceramic article according to any one of claims 1 to 3, characterized in that the microtexture has a maximum peak height Sp of 0.7 to 10.0 μm, preferably 0.8 to 5.0 μm.

5. The glass-ceramic article according to any one of claims 1 to 4, characterized in that the microtexture has a maximum valley depth Sv of 0.7 to 10.0 μm, preferably 0.8 to 5.0 μm.

6. The glass-ceramic article according to any one of claims 1 to 5, characterized in that the proportion of the surface occupied by the region located at a depth of 0.8 μm or more with respect to the maximum peak height Sp is 2 to 8%, preferably 2 to 4%.

7. The average area of the grains is 2×10 －３ mm ２ to 10×10 －３ mm ２ , preferably 3×10 －３ mm ２ to 8×10 －３ mm ２ , and the glass-ceramic article according to any one of claims 1 to 6 is characterized in that it is so.

8. The glass-ceramic article according to any one of claims 1 to 7, characterized in that the lower surface has an elliptical droplet-shaped portion with a height of 60 to 120 μm, preferably 80 to 100 μm.

9. The glass-ceramic article according to claim 8, characterized in that the droplet-shaped portion below the substrate has a spacing of 250 to 500 μm, preferably 300 to 400 μm in the vertical direction when measured between the edges.

10. The glass-ceramic article according to any one of claims 1 to 9, characterized in that the gloss difference between the worn area and the non-worn area is less than 20% in absolute value, preferably less than 15%.

11. A method for manufacturing a glass-ceramic article according to any one of claims 1 to 10, by roll-treating mother glass between two rollers, wherein one of the two rollers is a roller that has been subjected to shot peening treatment with a particulate material having a Vickers hardness HV1 of 3 to 10 GPa, preferably 4 to 8 GPa, and the mother glass thus roll-treated is subsequently subjected to a ceramization process.

12. The method according to claim 11, characterized in that the roller subjected to the shot peening treatment has a roughness Ra of 0.6 to 1.2 μm, preferably 0.8 to 1 μm.

13. The method according to any one of claims 11 and 12, characterized in that the roller subjected to the shot peening treatment has a roughness Rt of more than 4 μm, preferably more than 8 μm.

14. The method according to any one of claims 11 to 13, characterized in that the roller subjected to the shot peening treatment is not subjected to a polishing treatment after the shot peening treatment.

Images