• 专利附录
  • 专利说明
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    • 专利摘要:
    The invention relates to a glass-ceramic substrate consisting of a transparent tinted glass ceramic LAS, having the following composition (in% by weight): A12O3 18 - 23 Li2O 3.0 - 4.2 SiO2 60 - 69 ZnO 0 - 2 Na2O + K2O 0.2 - 1.5 MgO 0-1.5 CaO + SrO + BaO 0 - 4 B2O3 0-2 TiO2 2.3-4 ZrO2 0.5-2 P2O5 0 - 3 SnO2 0 - <0.6 Sb2O3 0 -1.5 AS2O3 0-1.5 TiO2 + ZrO2 + SnO2 3.8-6 V2O5 0.01-0.06 Fe2O3 0.03-0.2 comprising a gradient layer with mixed crystals of keatite and a core underlying mixed crystals of beta-quartz as the predominant crystalline phase, where the mixed keatite crystal, at a depth of 10 μm or more, exceeds 50% of the sum of the mixed quartz beta and mixed crystal proportions of kéatite. For this purpose, the ceramization comprises a crystal transformation step, in which the mixed quartz beta crystal is partially converted into mixed keatite crystal at a maximum temperature in the range of 910 ° to 980 ° and for a period of between 1 and 25 minutes.
    公开号:FR3030489A1
    申请号:FR1563281
    申请日:2015-12-23
    公开日:2016-06-24
    发明作者:Falk Gabel；Oliver Hochrein；Evelin Weiss；Roland Dudek；Uwe Martens
    申请人:Schott AG；
    IPC主号:
    专利说明:

    [0001] TECHNICAL FIELD The present invention relates to a glass-ceramic substrate consisting of a transparent tinted glass ceramic LAS, comprising a graded layer and an underlying core. The core presents the keatite mixed crystal (KMK) as the predominant crystalline phase, and the gradient layer exhibits mixed quartz beta crystal (HQMK) as the predominant crystalline phase. On the other hand, the invention relates to a method of manufacturing the glass-ceramic substrate and the use thereof. The manufacture of LAS vitroceramics of the type cited is carried out in several stages. During their industrial manufacture, it is known to first prepare by melting the crystallizable starting glass of the Li 2 O -Al 2 O 3 - 5iO 2 system, from a mixture of debris and powder mixture raw materials, to temperatures usually between 1500 ° C and 1650 ° C. When melting, refining agents such as arsenic, antimony and / or tin oxide are generally used. The use of 5nO2 in connection with high temperature refining above 1700 ° C is described by way of example in DE 199 39 787 C2. After melting and refining, the glass is usually hot-rolled or floated to make plates. For an economical manufacture, it is on the one hand desirable to obtain a low melting temperature and a low working temperature VA, and secondly the glass must not exhibit devitrification during forming. This means that parasitic crystals must not form, which can impair the strength and aesthetics of the starting glasses and glass-ceramics made therefrom. Since the forming is carried out around the operating temperature VA (viscosity 104dPas) of the glass, it must be ensured that the higher devitrification temperature of the melt is close to the processing temperature and advantageously lower than this, in order to avoid the formation of parasitic crystals. Then, the starting glass is converted in known manner by controlled crystallization to obtain the glass-ceramic article. This ceramization is generally carried out in the context of a two-stage process, in which germs are first produced by germination at a temperature of between 680 ° C. and 800 ° C., usually from mixed ZrO 2 crystals. / Ti02. It is also possible that Sn02 participates in germination. During the subsequent rise in temperature, it is first of all the mixed crystals of beta quartz that grow on these germs. High crystal growth rates, as desired for rapid and economical ceramization, are achieved for most compositions in the temperature range of 850 ° C to 1200 ° C, depending on the type of structure. At this maximum manufacturing temperature, the structure of the glass-ceramic is homogenized and the optical, physical and chemical properties of the glass-ceramic are adjusted. In the literature, the mixed beta quartz crystal is also referred to as "beta quartz" or "beta eukryptite". It is also known that mixed quartz beta crystals in the Li 2 O -Al 2 O 3 -SiO 2 system can be converted into a mixed keatite crystal by means of an additional ceramization process. The mixed crystal of keatite is also called "spodumene beta". For most compositions, the mixed keatite crystal transformation takes place at temperatures up to 1200 ° C, by irreversible reconstructive phase transformation. As is known, with this phase transformation, the crystals grow appreciably and thus form diffusion centers which result in translucency or opacity of the glass-ceramics. On the other hand, with the transition from quartz beta to mixed crystals of keatite, the coefficient of thermal expansion increases.
    [0002] For the purposes of the present application, "transparent" is understood to mean glass-ceramics which, compared with "translucent" or "opaque" glass-ceramics, have only negligible proportions of scattered light in the visible wavelength range. Transparency therefore means "clarity" of the glass ceramic, as opposed to its "cloudiness". Transmission losses occurring in this context are due to refraction on the crystals, phase boundaries or inclusions and therefore constitute wavelength-dependent volume effects. Whereas a "translucent" LAS glass ceramic has a proportion of diffuse light ("Haze") of more than 20% for a wavelength of 470 nm, measured in accordance with the international standard ISO 14782 1999 (E) and standardized for a 4 mm thick glass ceramic, a "transparent" LAS glass ceramic has a proportion of diffuse light that does not exceed 20 ° A. For the purposes of the present application, the term "tinted" is understood to mean a LAS glass ceramic which, because of one or more metal oxides or coloring colloids in its composition, exhibits transmission losses in the range of visible wavelengths, which are due to absorption. Here too, it is a question of wavelength-dependent volume effects. In particular, the coloring may be so dark that non-luminous objects are not visible to the naked eye through the LAS glass ceramic, while bright objects are visible. Therefore, a tinted glass ceramic may be opaque and, according to the above definition, at the same time "transparent". A typical application of the glass-ceramic of the type cited are, for example, hobs for which the requirements concerning the transmission behavior during practical use are very specific and sometimes even opposite. For example, to prevent unwanted view of the technical components through the glass ceramic hob and to avoid the glare effect of radiant heating elements, especially bright halogen heaters, the glass ceramic hobs are limited in their integral transmission. On the other hand, the radiant heating elements must be clearly visible during operation, even at reduced power. On the other hand, the display capacity also requires a certain degree of light transmission, for example when light-emitting diodes are installed under the hob. In order to meet these requirements, ceramic hobs are usually set to Tvis integral transmission values ranging from 0.5% to 5%. This is achieved by adding coloring elements. Regardless of the coloring element used, the glass ceramic hobs appear black, seen from above, because of the low light transmission, but, in transparency, appear mostly red, red-purple or orange-brown, following the coloring element used. An older type of ceramic hob, known as Ceran Color, manufactured by SCHOTT AG, had good color display capability. Ceran Color® is colored by the addition of NiO, CoO, Fe203 and MnO and refined with Sb203. This combination of coloring oxides makes it possible to set an integral light transmission which is typically 1.2% for conventional 4 mm thick baking planes. Depending on the wavelength, the transmission in the range of 380 nm to 500 nm is 0.1 to 2.8%. For a wavelength of 630 nm which is typical of red light emitting diodes, the transmission is about 6%. This former type of vitroceramic hobs has the disadvantage that the coloring oxides used also absorb very strongly in the infrared. IR transmission at 1600 nm is less than 20%. As a result, the cooking start speed is reduced. The transmission curve of Ceran Color® is shown in the book "Low Thermal Expansion Glass Ceramics", Hans Bach Collection Director, Springer Verlag Publishing Berlin Heidelberg 1995, page 66 (ISBN 3-540-58598-2). The composition is set forth in "Glass Ceramic Technology", Wolfram Holland and George Beall, The American Ceramic Society 1001, in Table 2-7.
    [0003] In the case of the newer, improved vitroceramic hobs, V205 is mostly used for coloring, as it has the particular property of absorbing in the visible light range and of allowing high transmission in the field of radiation. infrared. Staining with V205 is a complex process. As has been shown in previous studies (DE 199 39 787 C2), the passage of vanadium oxide in the dye state requires a redox process. In the crystallizable starting glass, the V205 has a relatively weak coloring effect and gives a slightly green shade. When ceramizing occurs the redox reaction, where the vanadium is reduced and the oxidation-reduction partner is oxidized. The refining agent acts as a primary redox partner. This has been demonstrated by Mössbauer studies on Sb-refined compositions as well as on Sn-refined compositions. During ceramization, part of the Sb3 + or Sn2 + in the starting glass passes to the higher oxidation step Sb5 + or Sn4 +. Vanadium is believed to be integrated in the reduced oxidation range, as V4 + or V3 +, in the seed crystal and produces intense staining by electron charge transfer reactions. TiO 2, as an additional redox partner, can also enhance vanadium oxide staining. In addition to the type and amount of the oxidation reaction partners in the starting glass, the oxidation-reduction state that is set in the glass upon melting also exerts an influence. A low oxygen partial pressure pO 2 - for example in a melt adjusted with a reducing effect by high melting temperatures - enhances the coloring effect of the vanadium oxide. Both LAS glass ceramics with KMK as the predominant crystalline phase and vitroceramics with HQMK as the predominant crystalline phase have long been known for various fields of application. For example, most of the commercial hobs consist of LAS glass ceramic with HQMK as the predominant crystalline phase. The proportion of crystalline phase of these glass-ceramics is as a rule between 55 and 80% by vol. The average crystallite sizes of the HQMK are on average less than 50 nm. For this reason, these glass-ceramics are transparent and can be tinted with coloring components, as described above. LAS vitroceramic hobs with KMK are more rarely used as the main crystalline phase. Glass-ceramics of this type are not transparent, especially in the wavelength range between 380 nm and 500 nm, but are translucent to opaque. Precisely in the presence of high temperatures, where the phase transformation for an economic industrial process proceeds rapidly, crystallites> 135 nm are formed which cause strong light scattering in the material. The phase content of the crystalline species of the translucent or opaque glass ceramic with KMK as the main crystalline phase is between 70 and 95% by vol. Concretely, for example, US Pat. No. 4,218,512 A discloses a translucent glass ceramic LAS with KMK as the predominant crystalline phase, as well as a manufacturing method thereof. Starting from a non-ceramised raw glass, the method described in this document comprises the steps of heating the glass product, up to a first temperature above 700 ° C at which a transformation into a glass-ceramic with HQMK as phase occurs crystalline predominant. Thereafter, the temperature is increased to a second value which is greater than 860 ° C, at which the mixed quartz beta crystals are converted into mixed keatite crystals, and the heating time and the holding time in this phase are maintained. many hours. This process behavior has economic disadvantages, since the total duration of the process is> 10 hours. For the exemplary embodiment cited, it was even indicated 10 hours. With this document, it is also known that it is thus possible to keep at the surface a layer with a thickness of about 40 μm, in which the HQMK continues to be present as the predominant crystal phase. On the other hand, it is known from this document that mixed quartz beta crystals have a coefficient of thermal expansion which is lower than that of mixed crystals of keatite.
    [0004] Another translucent glass ceramic with KMK as the predominant crystalline phase is known from EP 1 170 264 A1. According to this document, the ceramization first took place at a crystallization temperature ranging from 750 ° C. to 900 ° C. to produce the HQMK phase and, after a further increase in temperature, in a range from 900 ° C to 1200 ° C to convert it into a KMK phase. This document also indicates that mixed quartz beta crystals form on the surface as the predominant crystalline phase. Particular attention is paid to the fact that at the surface there is no transformation into a quartz structure a, to avoid too much tension in the surface, which could also create a tendency to crack in the surface and therefore a weakening of the material. Another document which discusses the type of translucent glass ceramic with KMK as the main phase is DE 200402458 Al, in which ceramization of the glass ceramic is also carried out in two stages. First crystallization of mixed quartz beta crystals is carried out at a temperature of 840 ° C, and then mixed keatite crystal transformation is carried out at a maximum temperature of between 1070 ° C and 1094 ° C. The impact strength of the glass-ceramic product thus produced is determined by an impact test of a ball on a glass-ceramic plate with a thickness of 4 mm, using a steel ball with a weight of 200 g, that one drops on a part of a test sample. Thus, fall heights causing rupture that were between 25 and 29 cm were determined. Translucent or opaque glass-ceramics with KMK as the predominant crystalline phase are also known from patent application US 2007/0213192 A1 which proposes a ceramization at a maximum temperature of 900 ° C. to 1050 ° C. and a holding time of at least 10 minutes. From US 4,211,820 it is also known that LAS glass ceramics with mixed crystals of keatite as the predominant crystalline phase are suitable as tinted glass ceramic for use as a hob. As is generally known, this document also emphasizes that the formation of KMK as the predominant crystalline phase in the vitroceramic core and the presence of HQMK as the predominant crystalline phase in the surface thereof lead to a consolidation of the whole glass ceramic, because of the distribution of the tensions. On the other hand, it is found that at ceramization temperatures of at most 900 ° C. to 950 ° C., a very low diffusion start can be observed. According to this document, the growth of beta spodumene crystals in the near-surface region should generally be avoided, otherwise translucent or even opaque products result. The document evokes a substantially transparent glass ceramic, but the crystal sizes determined are indicated to be less than 1 iam and mostly less than 500 nm, which effectively corresponds to a translucent glass ceramic as defined above. Another document which discusses a translucent glass ceramic with KMK as the predominant crystalline phase in the core and HQMK as the predominant crystalline phase in a gradient layer is DE 10 2010 006 232 A1. During ceramization, the glass product is rapidly heated to a maximum temperature of 1080 ° C. to 1300 ° C. is maintained for a maximum of 2 minutes at this maximum temperature or is preferably cooled immediately to room temperature. This makes it possible to manufacture glass-ceramics with high resistance to shocks and temperature variations and with a white level L *> 95. Lastly, document US 2014/0238971 A1 deals with a glass-ceramic with mixed crystals of keatite as phase main crystalline. In this document, it can be seen that the glass-ceramic may also contain a part of mixed quartz beta crystals. The ceramization takes place at a maximum temperature of 950 ° C to 1060 ° C, for a period of time of 5 to 15 min. The glass composition contains Fe 2 O 3 together with Cr 2 O 3 as coloring components, in order to obtain a brown-gray coloration after the ceramization. It is intended to achieve a white level L * between 25 and 45, that is to say a translucent to opaque glass ceramic. As for the above-mentioned exemplary documents relating to translucent glass-ceramics with KMK as the main crystalline phase in the heart, there are also a large number of disclosures concerning vitroceramics with HQMK as the predominant crystalline phase in the core. By way of example, DE 10 2008 050 263 A1 will be indicated here. The glass-ceramic disclosed therein is transparent and tinted. The ceramization takes place at a maximum temperature of 940 ° C, with a holding time of at most 15 min. From document DE 10 2007 025 893 A1, it is also known that it is also possible to manufacture LAS glass-ceramics with mixed crystals of keatite as the predominant crystalline phase, which are transparent. More specifically, this document relates to a glass ceramic with mixed crystals of keatite as the predominant crystalline phase, in a proportion ranging from 60 to 98% by vol., Which is intended as antiballistic shielding and therefore requires particularly high strength. At the same time, this document states that the appropriate choice of starting glass and temperature control during ceramization also makes it possible to manufacture such a glass-ceramic in a transparent form in the sense of the Andrejew Hoppe model and in the sense of the Rayleigh Ganz model. It is believed that the formation of small crystals with a mean crystal radius <30 nm is responsible for the transparency. On the other hand, in particular the ZnO component makes it possible to adjust the refractive power difference of the KMK crystallites with respect to the residual glassy phase. which is also useful for optimizing transparency. The ceramic hob is not tinted. Summarizing the results, it can be seen that on the one hand the ceramization conditions have an influence on the light scattering related to the formation of KMK and that on the other hand high ceramic temperatures and longer ceramization times lead to to a more intense coloration due to the vanadium oxide content. These two aspects can have negative effects on the display capacity. On the other hand, the transmission behavior of colored glass ceramics depends for both aspects of the wavelength. For this reason, efforts to improve the ease of use and technical functions of the apparatus by multicolored displays of as varied colors as possible and / or to offer the apparatus manufacturers the possibility of differentiating them by means of colors, regularly come up against technical difficulties. For the display capacity, for example so-called "seven-segment" or TFT displays, it would be important, in addition to a good adjustment of the absorption, to obtain a low diffusion of light in the material. A number of centers of diffusion too important in the material makes that the display is vague and is therefore disadvantageous for this application. In addition to transparency and coloring, vitroceramics intended for cooking surfaces must have many other properties. In particular, it is important to obtain a coefficient of thermal expansion as low as possible (designated CTE or a) because it strongly influences the TUF (resistance to temperature changes). LAS vitroceramics with HQMK as the main crystalline phase are characterized by a very low CTE (20/700 ° C), from about 0 to 0.5 ppm / K, and LAS vitroceramics with KMK as the main crystalline phase are characterized by a CTE (20/700 ° C) slightly higher, from about 0.8 to 1.5 ppm / K. On the other hand, the mechanical strength - above all the impact resistance - of the hobs plays an important role. To meet the requirements for shock resistance, in accordance with national and international safety standards, such as EN 60335 or UL 858 or CSA 22.2, LAS ceramic hobs must generally have material thicknesses of 3.8 mm. . Basically, thinner flat glasses would be desirable already for reasons of economy of material, but on the other hand, the thickness increases the impact resistance. However, the bending of the hob occurring in the event of impact, and the associated tensile stresses on its underside, increase substantially as the thickness of the hob decreases. Therefore, for thinner cooktops to meet the requirements of the impact resistance standards, the underside of the hob must have increased strength that is sufficient to withstand the higher tensile stresses.
    [0005] Therefore, the object of the present invention is to provide a glass-ceramic and a method of manufacturing the same, which use the least possible material and also have sufficient optical transparency and a possibility of coloring for a large number of applications. . This object is achieved by a glass-ceramic substrate consisting of a transparent tinted glass ceramic LAS having the following composition (in% by weight): Al 2 O 3 18 - 23 Li 2 O 3.0 - 4.2 SiO 2 60 - 69 ZnO 0 - 2 Na2O + K20 0.2-1.5 MgO 0-1.5 Ca0 + Sr0 + Ba0 0-4 B203 0-2 TiO2 2.3-4 ZrO2 0.5-2 P205 0-3 SnO2 0- <0, 6 Sb203 0 - 1.5 As203 0 - 1.5 Ti02 + Zr02 + SnO2 3.8 - 6 V205 0.01 - 0.06 Fe2O3 0.03 - 0.2 and optionally other coloring oxides, in total up to at a maximum of 1.0% by weight, comprising a gradient layer and an underlying core, in which the LAS glass-ceramic has the predominant crystalline phase in the keatite mixed crystal (KK) core, and in the layer graded crystalline quartz crystal (HQMK) as the predominant crystalline phase, and in which, for any point at a depth greater than or equal to 20 μm, preferably at any point at a depth greater than or equal to 15 i.tm and from particularly advantageous for any point located at a depth greater than or equal to 10 μm, the proportion of KMK crystalline phase exceeds 50% of the sum of the crystalline phase proportions HQMK and KMK.
    [0006] For simplicity, the following description uses the term "glass ceramic according to the invention" instead of "glass-ceramic substrate according to the invention", although it is not intended to refer to the material "glass-ceramic", but precisely the substrate made from it.
    [0007] Surprisingly, it is possible to manufacture from a LAS glass ceramic whose structure or crystalline layer profile is adjusted in the manner described above and which was carried out by the process described above. hereinafter, a glass-ceramic substrate which has a combination, not heretofore described, of a high resistance and of an appropriate coloring possibility in the visible wavelength range, while having a low diffusion (Haze ). For this reason, the substrate according to the invention is particularly suitable for applications such as cooking plates, with a thickness of less than 3.8 mm, preferably less than 3.2 mm thick, and with sufficient optical transparency. for the operation of light codes and display devices. The glass-ceramic substrate according to the invention, consisting of a LAS vitroceramic transparent tinted with the aforementioned composition and with a gradient layer close to the surface and an underlying core, where the glass-ceramic LAS present in the heart mixed crystals of keatite (KMK) as the predominant crystalline phase, and, in the gradient layer, mixed crystals of beta-quartz (HQMK) as the predominant crystalline phase, can therefore be defined by an impact resistance expressed by a "CIL" value of minus 0.8 N, where the CIL value corresponds to the aforementioned load of at least 0.8 N, with which, under 10% ambient humidity, a Vickers test machine is driven into the surface of the glass-ceramic, where on average 2 cracks, starting from the edges of an impression thus produced, are formed in at least 10 tests. It is well known to those skilled in the art that ambient humidity has an influence on the CIL value due to the physical phenomenon of stress corrosion cracking. For example, this may have the effect that the same glass ceramic substrate measured at a lower ambient humidity has a higher CIL value than in the case of a higher ambient humidity. So ; the glass-ceramic substrate according to the invention preferably has a CIL value of at least 0.98N in case of an ambient humidity of 1%.
    [0008] Thanks to the increased specific resistance, it is for the first time possible to produce a tinted glass ceramic with a thickness of only 3 mm, not exceeding in any case not more than 3.2 mm, with the same total permissible load as ceramic hobs. traditional with a thickness of 4 mm. This results in a potential material saving of at least 20% or, at equal thickness, a corresponding increase in strength. In addition, it is possible to dispense with "dents" on the underside of the hob, which are commonly used inter alia to increase the resistance. Thus, the glass-ceramic substrate according to the invention is advantageously made so as to be smooth on both sides. These advantages and other advantages and properties of the glass-ceramic substrate according to the invention and of the process according to the invention will be described below with the aid of the drawings, in which FIG. 1 represents a graph illustrating the determination of the breaking strength according to the "CIL" test; FIG. 2a represents a graph for comparing the tensile strength determined according to the CIL test under an ambient humidity of 10% and after a ball impact test on two samples in accordance with the invention and on a sample of comparison; FIG. 2b represents a graph for comparing the tensile strength determined according to the CIL test under an ambient humidity of 1% and after a ball impact test on two samples in accordance with the invention and on a sample of 3 is a graph of the proportions of crystalline phase HQMK and KMK as a function of depth, measured on a first sample according to the invention and measured by XRD of thin layers; FIG. 4 represents a graph of the proportions of crystalline phase HQMK and KMK as a function of the depth, measured on a second sample according to the invention and measured by XRD of thin layers; Fig. 5 is a graph of HQMK and KMK crystalline phase proportions as a function of depth, measured on a comparison sample; FIG. 6 represents a graph of the scattered light measurement, on two samples of the glass-ceramic according to the invention and on two comparison samples; and FIG. 7 represents a temperature-time graph illustrating the ceramification parameters necessary for the manufacture of the glass-ceramic according to the invention.
    [0009] In order to determine the breaking strength, the test method "Charge initiation load" ("CIL") known per se is used first; see for example US 8,765,262, A. It provides that a sample of the glass ceramic which is fixed in a nitrogen-swept medium is subjected to a point load using a material testing device (Mikro Kombi Tester from CSM) with a Vickers indenter VI-03. The predefined load is increased linearly within 30 seconds to a selected maximum value, and is reduced without maintenance in the same amount of time. Given the stress, it is possible that 0 to 4 cracks are formed in the glass-ceramic starting from the corners of the pyramidal impression. The selected maximum load value is increased in steps until 4 cracks are formed for each footprint. For each force, at least 10 measurements are taken to detect the change in crack formation which also depends on the existing surface (previous damage). The number of cracks for the same force is used to form a mean value. During the measurement, the sample preferably remains in the support until the crack count. The analysis is preferably carried out under a nitrogen atmosphere in order to avoid, as far as possible, subcritical growth of the cracks as a result of the humidity of the ambient air. Thus, it is determined in several tests the respective number of cracks propagating from the angles of the Vickers indenter footprint, depending on the applied load. The number of cracks determined are related to the impression force and reported in a graph, and an adjustment of a Boltzmann function is performed on the load / crack curve, as shown in Figure 1. Finally, we read on this curve the CIL value of the load which causes on average two cracks and is emitted as a characteristic for the impact resistance. FIG. 1 represents, by way of example, three measurement points.
    [0010] According to the invention, the load determined at 10% ambient humidity is at least 0.8N, and the load determined at an ambient humidity of 1% is at least 0.98N. However, the resistance of the glass-ceramic according to the invention and in particular the impact resistance which is important for the glass-ceramic substrate of a hob - cf. EN 60335, UL 858 or CSA 22.2 - can also be determined in another way. Another recognized test method for determining the impact resistance is the so-called "ball impact" test; cf. for example DE 10 2004 024 583 A1. It is carried out on square portions of dimensions 100 mm × 100 mm of a glass-ceramic plate to be tested. Measurement of impact resistance is based on DIN 52306. For this purpose, the measuring sample is placed in a test frame, and a steel ball of one weight is dropped. 200 g and a diameter of 36 mm in the center of the sample. The height of fall is increased gradually until there is a break. Because of the statistical nature of the impact resistance, this test is performed on a series of at least 10 samples. As characteristics of the resistance, the average value, the standard deviation and / or the 5% quantile of the distribution of the measured values are determined. This last value indicates to which height of fall 5% of the tested samples were broken. It is known that the impact resistance of a glass or glass-ceramic plate is determined inter alia by more or less random surface deteriorations. The effect of surface deterioration on the resistance, which is difficult to control because of its random nature, generally results in a large standard deviation of the measured value distribution and can therefore significantly distort a comparative evaluation of the batch impact strength. different test. One possible solution is to increase the statistical scope of the test, which may involve considerable expenditure if necessary. Another possibility which is recognized in expert circles is to subject the surface of the glass or glass-ceramic plate to a preliminary surface treatment, identical for all the test batches, in the form of deterioration. defined prior. In the examples given below, this preliminary deterioration consists of a single scratch which is made in the middle on the lower face of the measurement sample, facing the point of contact of the ball impact on the upper face. The scratching is carried out using a diamond tip, in this case a Knoop penetrator, by passing this diamond point, parallel to its longitudinal axis, in a straight line on the surface of the measuring sample, with a constant support force of 0.12 N and a constant speed of 20 mm / min over a length of at least 10 mm. The impact resistance of the LAS glass ceramic thus damaged by contact can be determined as described at the beginning, using the ball impact test. The standard deviation, which is typically less than 10% in relation, is then small, so that the measurement can be subjected to reliable statistical evaluation, while maintaining the size of the test batches at a reasonable level. The measurement results determined with the described CIL test and the described ball impact test are recorded in relation to each other in two graphs in Figures 2a and 2b, for comparison. In each case, two vitroceramics or two vitroceramic substrates A1 and A2 in accordance with the invention were tested and a comparison ceramic Bi with HQMK as the predominant crystal phase in the core. While the CIL measurements according to Fig. 2a were conducted at 10% ambient humidity, the CIL measurements according to Fig. 2b were conducted at 1% ambient humidity. Ball drop tests were carried out under everyday conditions at an ambient humidity of about 50% and were not modified, since ambient humidity has no influence. significant on bullet impact resistance. The results of the CIL tests are shown on the abscissa and those of the ball impact test on the y-axis. The average determined with the ball impact test, represented as round measuring points connected by a solid line, is entered as well as the 5% quantile, represented in the form of triangular measuring points connected by a line of measurement. dashes. There is a significant coincidence of the characteristics determined by the two methods. As expected, the 5% quantile is slightly lower than the respective associated measured value of the drop height. The pair of measuring points on the left represents the comparison ceramic B1 and the two pairs on the right represent respectively one of the embodiments A1 and A2. With both methods of measurement, it turns out that the two glass-ceramics having the layer structure according to the invention are much more resistant to rupture than the comparison ceramic. Thus, for a hob with a thickness of 4 mm, was measured in the embodiment according to the invention Al, with the ball impact test, a shock resistance of 46 + 6 cm. (average value + standard deviation) and 37 cm (quantile 5%). On the other hand, for the reference product B1 in transparent tinted glass ceramic, with HQMK as the predominant crystalline phase also in the core, only 19 + 3 cm (mean value + standard deviation) and 14 cm (quantile 5%) were determined by comparison. . Compared to the comparison example at A2, the height of fall could even be increased by about 90% and for Al by about 142%. The two exemplary embodiments clearly exceed the required CIL limit value of 0.8 N for an ambient humidity of 10% or 0.98 N for an ambient humidity of 1%.
    [0011] Not only for the comparison ceramic Bi, with HQMK as the predominant crystalline phase in the core, but also for known translucent or opaque glass-ceramics, with KMK as the main crystalline phase, the impact resistance after a predetermined deterioration is in a range significantly lower than for the glass ceramic according to the invention or the glass-ceramic substrate. For example, in the manner described in Examples B2 and B3, which are described later in Table 2, a ball impact test of the type described above was used to determine a fall height of only 29 + 6. cm.
    [0012] The limit value CIL of 0.8 N for an ambient humidity of 10% or of 0.98 N for an ambient humidity of 1% corresponds to an average height of approximately 32 cm and to a quantile 5% of approximately 26 cm. during the ball impact test. For this reason, the ball drop height, which is determined during the ball impact test on a vitroceramic according to the invention, previously degraded in a defined manner, as described above, is preferably from minus 30 cm (average value) and / or 25 cm (quantile 5%), and particularly advantageously at least 40 cm (average value) and / or 35 cm (quantile 5%). While the measurement of impact resistance as a standard requirement for hobs - again referred to EN 60335, UL 858 or CSA 22.2 - is of direct importance, there is no definition normative for the flexural strength as an additional parameter for characterizing the mechanical strength, but the determination of the flexural strength is another suitable measuring variable for demonstrating an increase in the resistance by the process according to the invention . The flexural strength test, which has been carried out additionally, is carried out as a double-ring test according to EN 1288 Part 5 (R45). In the flexural strength test with subsequent evaluation according to the Weibull model, a glass ceramic hob with a thickness of 4 mm according to the embodiment according to the invention achieves a characteristic flexural strength of 236 MPa for a Weibull module of 6.0. Compared to the same thickness comparison ceramic, with HQMK as the predominant crystalline phase in the core with a characteristic flexural strength of 171 MPa for a Weibull modulus of 7.3, this represents a significant increase and confirms the effect, generally favoring the resistance, of the layer structure according to the invention and of the crystal contents. The use of the Weibull model for the statistical exploitation of resistance measurements is generally known in expert circles, for example by W. Weibull, "A statistical theory of the strength of materials", IngeniôrsvetenskapsakademiensHandlingar N °. 151, 1-45 (1939). To compare, the flexural strength on B2 was also determined in this way. The result confirms: the Weibull evaluation gave a value of 131 Mpa, which is even lower than the value for HQMK glass ceramic. Consequently, all the analysis methods confirm that the specific resistance and in particular the specific impact resistance, which plays a preponderant role for use as a hob, is extremely high for the glass-ceramic of the substrate according to the invention, which makes it possible to obtain an overall resistance comparable to that of conventional glass-ceramic plates with a thickness of 4 mm, already from a thickness not exceeding 3.0 mm.
    [0013] This is due to the specific structure of the crystalline layers or the profile of the glass-ceramic, the determination of which will be explained hereinafter. The proportion of crystalline phase KMK and the proportion of crystalline phase HQMK as a function of depth are measured. The proportions of crystalline phase are here always indicated in% in flight. and average crystallite sizes in nm. The proportions of crystalline phase are determined by XRD thin films (X-ray diffraction) on intact samples of glass-ceramics or powdered XRD, on powders obtained from them. The characteristic reflections of the respective crystalline phase (HQMK or KMK) were measured and the proportion of crystalline phase was determined from the integral surface of the reflections. These integral surfaces were brought into contact with those of standard samples of known phase content, and the proportions of the crystalline and other amorphous phases were calculated in X-rays. The crystallite sizes given here were determined by Scherrer formula, in relation to a standard. Experience has shown that the relative measurement errors are 10% for the phase content and 5% for the crystallite size.
    [0014] FIGS. 3 to 5 show respectively a graph or a concentration profile of the crystalline phase proportions HQMK and KMK as a function of the depth, measured on a first example of a sample Al according to the invention (FIG. 3), a second example of a sample A2 according to the invention (FIG. 4) and an example of a comparison of a ceramic B1 with HQMK as the predominant crystalline phase in the core (FIG. 5). The proportions of the crystalline phase are reported respectively in% in the y direction, and the depth, starting from the surface of the glass-ceramic sample, is plotted in i.tm in the x direction. Vitroceramics were measured by X-ray diffraction with grazing incidence at 0.5 °. Experience shows that the depth information of such a measurement is of the order of about 2 μm. Then, the samples were successively polished and again measured by XRD, in order to determine the phase contents in deeper layers. The graphs show that in the embodiments A1 and A2, the proportion of HQMK first increases in a first part. This increase is due to the known vitreous zone, from a thickness of some 100 nm to a maximum of 1 μm, which is located on the surface of the glass-ceramic and which does not contain crystals. However, since the measurement DRX integrates during each measurement step on a depth information of about 2 i.tm, the content of HQMK in the first 2 i.tm enters the value measured on the surface which is not therefore not defined by 0% in the context of the measurement error. In the direction of the heart, the proportion of the HQMK phase then decreases successively, and at the same time the proportion of KMK increases respectively in the direction of the heart. In the case of Al, the proportion of KMK at about 76 i.tm corresponds to the proportion of the "volume value" (bulk) of about 75% which is determined at a depth of 2000 i.tm. At the same time, HQMK at 76 i.tm fell to the volume value at 2000 i.tm depth, which is 0%. In the case of embodiment A2, the proportion of HQMK decreases only up to 10%, and the volume value at a depth of 2000 i.tm is reached at about 56 i.tm. Correspondingly, at this depth the maximum value for KMK is reached with 59 ° A. Moreover, the layers contain so-called "X-ray amorphous" phases, that is to say phases that can not be detected by X-ray diffraction, which include, inter alia, also the vitreous phase. Both exemplary embodiments show that the point of intersection of the curves which represent the proportions of HQMK and KMK phase is between 0 and 10 i.tm, more precisely between 2 and 8 i.tm and thus in all cases below of 10 i.tm. In other words, at the latest at a depth of 10 μm and more, the proportion of KMK crystalline phase exceeded 50% of the sum of the crystalline phase proportions HQMK and KMK. On the other hand, in comparison example B1 it is clearly seen that there is no KMK in the material and that HQMK reaches its maximum volume value of 70% already at 29 i.tm at a depth of 2,000. i.tm. At the same time, despite the formation of KMK in the core, the glass-ceramic according to the invention is transparent and, because of the absence of troublesome diffusion centers, therefore, in principle is also particularly suitable for multicolor displays. The transparency is determined by a light measurement diffused according to the international standard ISO 14782 1999 (E), standardized respectively for a vitroceramic of a thickness of 4 mm.
    [0015] In Fig. 6, the result of this scattered light measurement is plotted in a wavelength range of 380 nm to 1000 nm. The measurement was carried out on the two samples A1 and A2 in accordance with the invention and on two comparison samples B1 and B3. While comparison sample Bi, with HQMK as the predominant crystalline phase in the core of the glass-ceramic, has as expected a proportion of low scattered light, hereinafter also called "Haze", of about 4% for a length of At 470 nm, the value for the translucent B3 comparison sample, with KMK as the predominant crystalline phase in the vitroceramic core, is about 27%, which is very high. On the other hand, the proportion of maximum diffusion of the glass-ceramics A1 and A2 according to the invention is about 9% and about 13% for a wavelength of 470 nm, determined respectively on an adjustment of the measured curves represented. in FIG. 6. In addition, the maximum diffusion proportion does not exceed the value of 17% in the entire wavelength range from 400 nm to 500 nm and is therefore in the field of transparency. .
    [0016] To ensure that the glass-ceramic is suitable for multicolored displays, the proportion of maximum scattered light ("haze"), determined according to the international standard ISO 14782 1999 (E), standardized for a glass-ceramic with a thickness of 4 mm and for a length wavelength of 470 nm, is therefore preferably at most 15%, particularly advantageously at most 12%. On the other hand, the proportion of maximum diffusion ("haze"), determined according to the international standard ISO 14782 1999 (E), standardized for a vitroceramic of a thickness of 4 mm, in a range of wavelengths from 400 nm to 500 nm, preferably does not exceed 20% and does not exceed particularly advantageously not more than 17%. In addition to transparency, while taking into account a good display ability, the glass-ceramic must still have sufficient coloration, that is to say, cause transmission losses by absorption in the range of visible wavelengths. In particular, the coloring must be so dark that non-luminous objects can not be distinguished with the naked eye through the glass ceramic LAS, while the luminous objects are visible. A measurement quantity that represents this property is the Tvis integral transmission in the visual spectral region Tvis, also called Y, "brightness" or "luminance", and is calculated from the transmission spectrum in the wavelength range of 380 nm at 780 nm. For this purpose, the measured spectrum is folded with the emission spectrum of a standard light source (D65) and with the green part of the "tristimulus" of the CIE color system. For the integral transmission of the glass-ceramic according to the invention in the visible spectral region, standardized for a vitroceramic Tvis <5 ° A. This setting of parameters constitutes a sufficient concealment of a thickness of 4 mm, preferably non-luminous components located under the glass-ceramic. On the other hand, the spectral transmission T470nm, 4mm of the glass-ceramic according to the invention, standardized for a glass-ceramic with a thickness of 4 mm, for a wavelength of 470 nm, is preferably greater than 0.1. AT. Finally, the spectral transmission T550nm, 4mm of the glass-ceramic according to the invention, standardized for a glass-ceramic with a thickness of 4 mm, for a wavelength of 550 nm, is preferably greater than 0.25 ° A. The two parameter settings listed last guarantee each one an improved color display capability, and together a particularly good display capacity. Thus, the invention combines for the first time properties so far considered as incompatible, such as a high resistance, on the one hand, and a good display capacity, due to poor diffusion and transmission properties. adapted, on the other hand. It is therefore particularly suitable for applications with high aesthetic requirements, such as hobs or displays and control areas. In this respect, the increased impact strength of the material makes it possible to manufacture hobs with smaller material thicknesses, for example 3 mm, which meet the requirements of EN 60335 and UL 858 or CSA 22.2.
    [0017] These properties, which seem to be partly opposed, are obtained by the joint action, closely coordinated, between the composition of the glass-ceramic, on the one hand, and the ceramization process, on the other hand.
    [0018] The method according to the invention for producing the glass-ceramic substrate according to the invention, from a glass LAS with the aforementioned composition, provides the following steps, starting from the molten glass: refining of the molten glass, formation of the raw glass with cooling of the molten mass, application to the raw glass thus produced, of a germination step, then of a crystal growth step in which HQMK crystals grow on the crystals of crystals, application to intermediate vitroceramic product thus precrystallized, comprising mixed crystals of beta-quartz (HQMK) as the predominant crystalline phase, in a crystal transformation step in which the crystalline phase HQMK is partially converted into a crystalline phase KMK, where the step of transformation of crystals is carried out with a maximum temperature Tmax and during a holding time t (Tmax) of this maximum temperature in a temperature-time range which is delimited by four straight lines connecting the four points of angle with the pairs of values (Tmax = 910 ° C; t (Tmax) = 25 minutes), (Tmax = 960 ° C, t (Tmax) = 1 minute), (Tmax = 980 ° C, t (Tmax) = 1 minute) and (Tmax = 965 ° C; Tmax) = 25 minutes).
    [0019] Starting from a precrystallized vitroceramic intermediate product comprising mixed quartz beta crystals (HQMK) as the predominant crystalline phase, the process according to the invention starts correspondingly with the crystal transformation step. And starting from a green glass, the process according to the invention starts correspondingly by the germination step which is followed by the crystal growth step and the crystal transformation step. The composition of the glass-ceramic, in connection with the manufacturing process, makes it possible to produce the aforementioned layer structure and crystal contents, as well as the transmission characteristic according to the invention and therefore the advantageous properties of the material. The main crystalline phase of the glass-ceramic is then composed of KMK which is present in the following composition range: Li (1-2,2y) Mg'ZnyAlSi206 -Li (1-2x-2y) Mg (x) Zn (y) AlSi4010 with (0 <x <0.5; 0 <y <0.5 and 0 <x + y <0.5). The ceramization program according to the invention for the transformation of crystals is explained with the aid of FIG. 7. The inventors have found that the glass-ceramics with the cited composition do not meet the desired properties until they have been ceramized in conditions in the trapezoidal temperature-time range shown in Fig. 7, which is delimited by four straight lines connecting the four corner points with the value pairs (maximum ceramization temperature Tmax, holding time t (Tmax)) indicated in Table 1 below. The preferred values are also shown in Table 1. Table 1 Tmax [° C] t (Tmax) [min] Angle Point 1,910, 25, preferably 920 preferably Corner Point 2,960 1, preferably 2 corner point 3980 1, preferably 2 corner point 4 965 25, preferably 20 by way of example, in the graph of FIG. 7, in which the holding time t (T max) is written by relative to the maximum ceramization temperature T max, are listed ceramics Al to A7 according to the invention and the comparison examples not encompassed by the invention. The temperature-time range of the ceramification parameters according to the invention is drawn in the form of a trapezoidal framed surface whose angles have the coordinates of Table 1. Preferably, the process according to the invention is improved by the the green glass or glass ceramic intermediate is heated from room temperature to maximum temperature T 1, for a period of not more than 60 minutes, preferably not more than 45 minutes and particularly advantageously up to 30 minutes. The advantage of this improvement lies in the fact that the ceramization conditions of the holding time t (Tmax) and the maximum ceramization temperature Tmax, determining for the properties of the product, in which the ceramization processes and above all the transformation in particular, are achieved quickly and ceramization does not take place during heating and therefore in a less controlled manner. For the manufacture of a high-strength transparent glass ceramic containing KMK, a much cheaper ceramization process has been developed because it is faster compared to the state of the art. This is apparent for example from the comparison with the processes described in US 20140238971 A. While the process according to the invention, including the time of cooling to a temperature of 780 ° C, requires in total less than 60 min, preferably less than 50 min, ceramification processes, which have been described by the state of the art, last at least 80 minutes to reach a comparable temperature in the range of the so-called "cooling curve", c ' that is to say of the phase following the maximum temperature. The short holding time at Tmax then ensures that the KMKs are formed with a dimensional distribution, a global average size and a proportion of phase which make it possible to obtain the high resistance, together with a low light diffusion and therefore the transmission according to the invention. This is all the more surprising since these ceramization conditions in accordance with the invention could also be combined with a more economical and faster process than that described in the state of the art. It also seems that 5nO2, as a germinating agent, plays a decisive role in the process of germination and growth. Thus, it has been observed that the transformation of an untinted transparent glass ceramic containing Sn into an opaque glass ceramic is substantially slowed compared with an As-refined glass ceramic. This also seems to be the case with the material and the process according to the invention, and for this reason it is possible to produce transparent glass-ceramics also in the wavelength range from 380 nm to 500 nm, which at the same time time a high proportion of keatite phase. This is due to the slow growth of the crystals and the small crystal sizes that result.
    [0020] The manufacturing can be made even safer from the point of view of the process, and the required product properties can be refined, if one respects the preferred parameters, described hereinafter. The glass-ceramic is preferably made from a LAS glass which, with the exception of unavoidable traces, is free of arsenic and antimony and usually contains at least 0.1% by weight of 5nO 2. Basically, DE 199 39 787 C2 discloses the use of 5nO2 as an ecological reducing agent (in contrast to 5b203 or As203) during refining and as an oxidation-reduction partner for a coloring oxide, such as V205 and / or Fe205 for the color of the glass ceramic. In particular, excellent color effects and bubble qualities can be achieved in combination with high temperature refining above 1700 ° C. As regards the coloring, it is particularly advantageous when the following condition is observed for the Fe.sub.2 O.sub.3 and V.sub.2 O.sub.5 components in the composition: ## STR1 ## On the other hand, with regard to the coloration, the ceramization conditions T. and t (Tmax) are chosen optimally such that there is no darkening of the already colored glass ceramic.
    [0021] In combination with a short germination time and a short volume crystallization, we do not go below a Tvis of 0.5%, although we go through three areas that can contribute to the coloring. and diffusion. Finally, it avoids diffusion because the short ceramization time "freezes" so to speak the state of low diffusion. The other coloring oxides in the composition include at least one of the group consisting of Cr, Mn, Co, Ni, Cu, Se, Mo, W, their oxides, and rare earth metal oxides. In particular, it is Cr 2 O 3, MnO 2, MnO, CoO, Co 2 O 3, NiO, Ni 2 O 3, CuO, Cu 2 O, SeO, other rare earth metal oxides and molybdenum compounds. If necessary, these coloring substances make it possible to adjust even more precisely the color locations and / or the transmission values. Preferably, the content of Cr 2 O 3 is less than 100 ppm, so as not to limit transmission too much, especially in the spectral region from 380 nm to 500 nm, which would have negative effects on the display capacity for white LEDs. and blue or color displays.
    [0022] Advantageously, the ZnO content is at least 0.2% by weight. ZnO is advantageous with respect to the refractive index adaptation between the crystalline phase and the glassy phase and is therefore positive for the transmission properties, due to the reduction of diffusion to a minimum. In addition, for undyinted vitroceramics, Zn-induced gahnite formation serves to improve the white L * level. The MgO content is preferably at least 0.1% by weight and particularly preferably at least 0.25% by weight. The upper limit of the MgO content is preferably 1% by weight. Preferably, the A1203 content is 19 to 23% by weight. The A1203 content plays a decisive role in the Al / Si ratio adjustment in KMK as well as in HQMK. This allows for example to adjust the coefficient of thermal expansion of the glass ceramic.
    [0023] On the other hand, A1203 has a positive effect on the chemical resistance of the glass ceramic. On the other hand, it has proved advantageous that the TiO 2 content is from 19 to 23% by weight.
    [0024] The content of ZrO 2 is from 0.5 to 1.9% by weight, preferably from 0.5 to 1.8% by weight and particularly advantageously from 0.5 to 1.7% by weight. Within these limits for TiO 2 and ZrO 2, the germination behavior is particularly advantageous. On the one hand, it must be ensured that there is a sufficient quantity of germinating agent (zirconium titanate) to guarantee rapid and uniform ceramization. On the other hand, levels of TiO 2 and especially ZrO 2 too high lead to devitrification or spontaneous germination, already during the formation of raw glass which also prevents homogeneous ceramization and good transparency. Preferably, the glass-ceramic substrate has a glass-surface area on the gradient layer, with a thickness of 50 to 1000 nm, preferably 50 to 800 nm and particularly preferably 300 to 800 nm. This layer, which is created by diffusion processes, in particular by Li diffusion in the volume or core, and thus causes an enrichment of Li inside and an impoverishment in the crystal surface area, is considered as positive especially in regarding chemical attack processes. It has been found to be advantageous for the crystalline proportion of all phases in the core to be at most 90%, preferably at most 85% and particularly preferably at most 80%. An advantageous lower limit may be indicated with at least 69 ° A. Other secondary crystalline phases are HQMK, rutile, gahnite and zirconium titanate. It has proved advantageous when the total proportion of keatite is less than 80%. The crystalline proportion is important for adjusting the properties of the glass ceramic, including thermal expansion. Since KMK has a higher thermal expansion than HQMK, the proportion of KMK should be limited in particular.
    [0025] In order to guarantee a sufficient transparency of the glass-ceramic substrate, the crystals of the KMK phase at the heart of the glass-ceramic are preferably <130 nm, determined as described above, by X-ray diffraction / X-ray measurement.
    [0026] The coefficient of thermal expansion cczonoo of the resulting glass ceramic is preferably less than 1.3x10-6 / K. Thus, it is in the range of known translucent LAS glass-ceramics, with KMK as the main crystalline phase. The resistance to temperature variations of the glass-ceramic substrate according to the invention is preferably> 800 ° C. On the other hand, the resistance to temperature variations of translucent KMK glass-ceramics is typically 700 ° C. Temperature Resistance (TUF) describes the resistance capability of a glass or glass-ceramic object in relation to a local temperature gradient. In connection with the use as a hob, the TUF test is defined as follows: a sample, consisting of a square portion of dimensions 250 mm x 250 mm of the glass ceramic plate to be tested, is placed horizontally on a radiant heating element, typical of such an application and having an outside diameter of 180 + 3 mm, being applied flat and asymmetrically positioned such that the four side media of the sample exceed 25 + 2 mm, 35 + 2 mm, 35 + 2mm, 45 + 2 mm from the outer edge of the heating element. A suitable radiant heating element is, for example, the heating element of type 200N8, D2830R from Ceramaspeed Ltd. with 2300 W / 220 V characteristics. When the heating element is operating, a temperature gradient is created between the heated zone and the cold outer edge of the sample. The heating operation of the heating element is controlled so that after 5.0 + 0.5 minutes there is a break due to the temperature gradient. The maximum temperature reached on the surface of the sample in front of the heating element is recorded as a characteristic of the TUF. Due to the statistical nature of the TUF, this test is performed on a series of at least 10 samples. The TUF of the sample lot is defined by the average value of the distribution of the measured values. It is known that the resistance of a glass or glass-ceramic plate to tensile stresses of mechanical or thermal origin depends inter alia on more or less random surface deterioration. As part of the application as a hob, it is likely that during its practical use, the glass or glass-ceramic plate will suffer surface deterioration, including abrasive cleaning and kitchen utensils. Therefore, a conclusion concerning TUF, in so far as it must be significant for the intended use, presupposes a prior deterioration of the measuring sample, which corresponds to the surface deterioration of a normal practical use. Experience has shown that this can be achieved by sanding the surface of the sample with 220 grit sandpaper at a pressing pressure of 1.2 N / cm. It is known to those skilled in the art that sanding actually acts on the breaking behavior only if it is carried out particularly in regions which exhibit tensile stresses during the test, and this in a sanding direction which is perpendicular to the main direction of the stresses. This includes sanding the cold edge of the sample in the middle region of its sides and perpendicular to its outer edges. The glass-ceramic substrate of the type described above is preferably used as a covering element for heating elements, in particular as a hob, as kitchen equipment, radiator covering element, grilling surface or chimney glass, heating plate. furnace support or lining in the ceramic, solar or pharmaceutical industry or medical technology, in particular for production processes under high purity conditions, as furnace lining in which chemical or physical coating processes are carried out or as chemically resistant laboratory equipment, as a glass-ceramic object for applications at high temperature or extremely low temperature, as a window for incinerators, as a heat shield for hot environments, as a covering element for reflectors, projectors, video projectors, photocopiers, po for applications with thermomechanical stresses, for example in night vision devices or as a wafer substrate, as a translucent object with UV protection, as a material for housing components, for example electronic devices and / or cover glasses for IT, for example mobile phones, laptops, scanner windows etc., or as a facade plate, as fireproof glazing or as a ballistic protection component. According to the inventors' studies, it may already suffice for only one component of the composition, the maximum temperature during the ceramization or the ceramization time to deviate from the range defined by the invention, so that the properties required for the glass-ceramic according to the invention or the glass-ceramic substrate made from it are not reached. Table 2 below shows the influence exerted by the joint action of the various parameters on the result.
    [0027] Table 2 compares 8 embodiment examples A0 to A7 with 4 comparison examples B1 to B4. For the composition of the glass ceramic LAS, the significant parameters of ceramization, namely the maximum ceramization temperature Tmax in ° C, the passage time "DLZ" in minutes, the holding time at the maximum ceramization temperature, have been indicated. t @ Tmax in minutes and the heating rate up to Tmax in Kelvin / minute. The parameters passage time, holding time and heating rate are first indicated respectively as "real" values, that is to say concretely how the ceramization of the example in question was carried out. Then, the "preferred ranges" of these three parameters are indicated, in which the ceramization for the concrete composition and the maximum ceramization temperature of the examples according to the respective invention is successfully carried out. Below are the production parameters measured according to the methods described above, in the following order:% HQMK phase content,% KMK phase content, HQKM average crystallite size in nm, average crystallite size from KMK in nm (the phase contents as well as the crystallite sizes refer respectively to the bulk of the glass-ceramic, measured on samples in powder form); subjective optical transmission properties (tinted, unstained), measured transmission at 470 nm wavelength, normalized for 4 mm thick glass ceramic, in%, measured Tvis integral transmission in the visible spectral region, normalized for a glass ceramic with a thickness of 4 mm, in%, maximum diffusion proportion ("Haze"), standardized for a glass ceramic with a thickness of 4 mm, for a wavelength of 470 nm, coefficient of thermal expansion OEzonowc between 20 and 700 ° C in 1 / K; resistance to temperature changes TUF in ° C; and impact resistance determined by a ball impact test and indicated as average value and as quantile 5%, respectively in cm, and determined by the CIL method and indicated in N. All the exemplary embodiments form KMK in the sense of the invention, that is to say that they comprise a proportion of KMK dominant phase in the heart. It is the same for the examples of realization B2 and B3. The other exemplary embodiments do not form a KMK or a quantity that is too small. By contrast, Examples B2 and B3 show that the crystals become too large, which is attributed to the maximum ceramization temperature, in relation to the holding time. As a result, these glass-ceramics are not transparent enough but are translucent. Example B1 shows that due to the weak formation of KMK the effect of increasing resistance is not obtained. The example therefore loses display capacity.
    [0028] Taolea Example 0 0.0: 7 - 10 L-xerrples-ealsaticri.1 J.50 1 11.
    [0029] Table I e-exe ru) t: IFIFc: IJ; 1 1: 215 I! ## STR1 ## FIG. 2 A: ## EQU1 ##
    [0030] 1 A2 A3>: Exeli-Lri_es reali.sia ce.-31-11.E.:511:01 Tr-1113x. - restored) ---; 1.> 57 78 c: 1.3 nr -rr Hyi = 471: 1 n a.411-n TUF Resistv.cee Li 1 -art Clt5 Table 2 _: extre-exe, nr: e A6 A7 refer4, e:. : ## EQU1 ## ## EQU1 ## 1: 712.0 & XIII. 3.0 1, 7 29.0 I-, 6.0 CIL_ 30 I 17: 7, ri 4r4 zprn C.11
    权利要求:
    Claims (18)
    [0001]
    REVENDICATIONS1. Glass-ceramic substrate consisting of a transparent tinted glass ceramic LAS having the following composition (in% by weight): Al 2 O 3 18 - 23 Li 2 O 3.0 - 4.2 SiO 2 60 - 69 ZnO 0 - 2 Na 2 O + K 2 O - 2 , 5 MgO 0-1.5 Ca0 + Sr0 + Ba0 0-4 B203 0-2 TiO2 2.3-4 ZrO2 0.5-2 P205 0-3 5nO2 0 - <0.6 5b203 0-1.5 As203 0-1.5 Ti02 + Zr02 + SnO2 3.8 - 6 V205 0.01 - 0.06 Fe2O3 0.03 - 0.2 and optionally other coloring oxides, in total up to a maximum of 1, 0% by weight, comprising a gradient layer and an underlying core, in which the LAS glass-ceramic contains keatite mixed crystals (KMK) in the core as the predominant crystalline phase, and, in the gradient layer, mixed crystals beta quartz (HQMK) as the predominant crystalline phase, and in which, at any point at a depth greater than or equal to 20 μm, the proportion of KMK crystalline phase exceeds 50% of the sum of the crystalline phase proportions HQMK and KMK.
    [0002]
    2. Glass ceramic substrate according to claim 1, characterized in that it has a breaking strength of the glass-ceramic, expressed by a CIL value of at least 0.8 N in the case of an ambient humidity of 10% and at least 0.98N in the case of an ambient humidity of 1%.
    [0003]
    3. Glass ceramic substrate consisting of a transparent tinted glass ceramic LAS, having the following composition (in% by weight): Al 2 O 3 18-23 Li 2 O 3.0-4.2 SiO 2 60-69 ZnO 0-2 Na 2 O + K 2 O 0.2 -1.5 MgO 0-1.5 Ca0 + Sr0 + Ba0 0-4 B203 0-2 TiO2 2.5-4 Zr02 0.5-2 P205 0-3 5n02 0 - <0.6 5b203 0-1, As203 0-1.5 TiO 2 + ZrO 2 + SnO 2 3.8-0.6 V 2 O 0.01-0.06 Fe 2 O 3 0.03 -0.2 and optionally other coloring oxides, totaling up to 15%. At most 1.0% by weight, comprising a graded layer and an underlying core, in which the LAS glass ceramic has keatite crystals (KMK) as the predominant crystalline phase in the core, and in the layer gradients, mixed crystals of beta-quartz (HQMK) as the predominant crystal phase, and in which the glass-ceramic has a resistance, expressed as a CIL value, of at least 0.8 N in the case of an ambient humidity of 10% and at least 0.98N in the case of an ambient humidity of 1%.
    [0004]
    Glass-ceramic substrate according to one of the preceding claims, characterized in that the concentration profile of the crystalline phase proportions HQMK and KMK and / or the resistance is achieved by phase transformation of HQMK crystals into KMK crystals during ceramizing at a maximum temperature Tmax and during a holding time t (Tmax) of this maximum temperature in a temperature-time range which is delimited by four straight lines connecting the four angle points with the pairs of values (Tmax = 910 °) C, t (Tmax) = 25 minutes), (T = 960 ° C, t (Tmax) = 1 minute), (Tmax = 980 ° C., t (Tmax) = 1 minute) and (Tmax = 965 ° C. t (Tmax) = 25 minutes).
    [0005]
    5. Glass ceramic substrate according to one of the preceding claims, characterized in that the maximum diffusion proportion ("haze"), standardized for a 4 mm thick glass-ceramic, for a wavelength of 470 nm, is at most 15%, preferably at most 12%.
    [0006]
    6. Glass ceramic substrate according to one of the preceding claims, characterized in that the maximum diffusion proportion, standardized for a glass-ceramic with a thickness of 4 mm, in a wavelength range from 400 nm to 500 nm, does not exceed 20% and preferably does not exceed 17%.
    [0007]
    7. Glass ceramic substrate according to one of the preceding claims, characterized in that the glass-ceramic is produced from a LAS glass which, with the exception of the inevitable traces, is free of arsenic and antimony and contains at least 0.1% by weight of 5nO2.
    [0008]
    8. Glass ceramic substrate according to one of the preceding claims, characterized by the condition 1 <Fe 2 O 3 / V 2 O 3 <8.
    [0009]
    9. Glass ceramic substrate according to one of the preceding claims, characterized in that the other coloring oxidesinclude at least one substance from the group consisting of elements Cr, Mn, Co, Ni, Cu, Se, Mo, W, their oxides and oxides. rare earth metals.
    [0010]
    10. Glass ceramic substrate according to one of the preceding claims, characterized in that the integral visual transmission in the visible range, standardized for a glass-ceramic with a thickness of 4 mm, is Tvis, 4mm less than or equal to 5%.
    [0011]
    11. Glass ceramic substrate according to one of the preceding claims, characterized in that the spectral transmission, standardized for a glass-ceramic with a thickness of 4 mm, is strictly greater than 0.1%, for a wavelength of 470 nm. and / or strictly greater than 0.25% for a wavelength of 550 nm.
    [0012]
    12. Glass ceramic substrate according to one of the preceding claims, characterized in that it comprises a vitreous surface area on the gradient layer with a thickness ranging from 300 to 1000 nm, preferably from 300 to 800 nm.
    [0013]
    13. Glass ceramic substrate according to one of the preceding claims, characterized in that the crystalline proportion in the core is at most 82%, preferably at most 80% and particularly advantageously at most 76%.
    [0014]
    14. Use of a glass-ceramic substrate according to one of the preceding claims, as a covering element for heating elements, in particular as a hob, kitchen equipment, radiator covering element, grilling surface, chimney glass, support plate or furnace lining in the ceramic, solar or pharmaceutical industry or medical technology, in particular for production processes under high purity conditions, as furnace lining in which chemical coating processes are carried out or as chemically resistant laboratory equipment, as a glass-ceramic object for applications at high temperature or extremely low temperature, as a window for incinerators, as a heat shield for hot environments, as a covering element for reflectors, projectors, video projectors, photocopiers, for applications with thermomechanical stresses, for example in night vision devices, as a wafer substrate, as a translucent object with UV protection, as a material for housing components, for example electronic devices and / or cover glasses for IT, for example, mobile phones, laptops, scanner windows, etc., as a facade plate, as fireproof glazing or as a ballistic protection component.
    [0015]
    15. ceramizing process for producing a glass-ceramic substrate according to one of claims 1 to 13, wherein a precrystallized vitroceramic intermediate product, with mixed crystals of quartz beta (HQMK) as predominant crystalline phase, based on a Li20-Al 2 O 3 -SiO 2 glass composition comprising (in% by weight): 0.01 - 0.06 Fe 2 O 3 0.03 - 0.2 and, if appropriate, other coloring oxides, in total up to to at most 1.0% by weight is subjected to a step of conversion of Al 2 O 3 18 -23 Li 2 O 3.0 - 4.2 SiO 2 60 - 69 ZnO 0 - 2 Na 2 O + K 2 O 0.2 - 1.5 MgO 0 - 1.5 Ca0 + Sr () + BaO 0 - 4 B203 0 - 2 TiO2 2.3 - 4 Zr02 0.5 - 2 P205 0 - 3 SnO2 0 - <0.6 Sb203 0 - 1.5 As203 0 - 1,5 TiO2 + Zr02 + Sn02 3,8 - 6cristal during which the crystalline phase HQMK is partially converted into a KMK crystalline phase, the transformation step being performed at a maximum temperature T.ax and for a time of holding t (Tmax ) of this maximum temperature in a temperature-time range which is delimited by four straight lines connecting the four corner points with the pairs of values (T 1 = 910 ° C; t (Tmax) = 25 minutes), (Tmax = 960 ° C, t (Tmax) = 1 minute), (Tmax = 980 ° C, t (Tmax) = 1 minute) and (Tmax = 965 ° C; Tmax) = 25 minutes).
    [0016]
    16. Ceramizing process for producing a glass-ceramic substrate according to any one of claims 1 to 13, wherein a green glass, on the basis of a Li20-Al 2 O 3 -SiO 2 glass composition comprising (in% weight) A1203 18 -23 Li2O 3.0 - 4.2 SiO2 60 - 69 ZnO 0 - 2 Na2O + K20 0.2 - 1.5 MgO 0 - 1.5 Ca0 + Sr () + Ba0 0 - 4 B203 0 - 2 TiO2 2,3 - 4 Zr02 0,5 - 2 P205 0 - 3 Sn02 0 - <0.6 Sb203 0 - 1.5 As203 0 - 1.5 TiO2 + Zr02 + Sn02 3.8 - 6 V205 0, 01 - 0.06 Fe203 0.03 - 0.2 and, if appropriate, other coloring oxides, in total up to a maximum of 1.0% by weight, is subjected to a germination step, then to a step of crystal growth, in which HQMKs grow on the crystal seeds, and then in a crystal transformation step, with the process characteristics of claim 15.
    [0017]
    17. A method of manufacturing a glass-ceramic substrate according to one of claims 1 to 13, comprising the following steps: melting of a Li20-Al 2 O 3 -SiO 2 glass composition comprising (in% by weight): A1203
    [0018]
    Li20 3.0 - 4.2 SiO2 60 - 69 ZnO 0 - 2 Na2O + K20 0.2 - 1.5 MgO 0 - 1.5 Ca0 + Sr0 + Ba0 0 - 4 B203 0 - 2 TiO2 2, 3 - 4 Zr02 0.5 - 2 P205 0 - 3 Sn02 0 - <0.6 Sb203 0 - 1.5 As203 0 - 1.5 TiO2 + Zr02 + Sn02 3.8 - 6 V205 0.01 - 0.06 Fe203 0.03 - 0.2 and, if appropriate, other coloring oxides, in total up to a maximum of 1.0% by weight, refining the molten glass, then forming a green glass with cooling of the glass bath melting, then ceramizing the green glass according to the process characteristics of claim 16. 18. Method according to one of claims 15 to 17, characterized in that the green glass or the vitroceramic intermediate product is heated for a period of time. at most 60 minutes, preferably at most 45 minutes and particularly advantageously at most 30 minutes, to go from room temperature to the maximum temperature Tmax.
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    同族专利:
    公开号 | 公开日
    CN105712632A|2016-06-29|
    EP3040318A1|2016-07-06|
    DE102014226986B9|2017-01-12|
    US10183888B2|2019-01-22|
    KR20160076995A|2016-07-01|
    DE102014226986A1|2016-06-23|
    CN105712632B|2021-08-03|
    JP2016155742A|2016-09-01|
    US20160176752A1|2016-06-23|
    DE102014226986B4|2016-11-03|
    EP3040318B1|2020-08-05|
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    法律状态:
    2016-12-22| PLFP| Fee payment|Year of fee payment: 2 |
    2017-12-21| PLFP| Fee payment|Year of fee payment: 3 |
    2019-12-19| PLFP| Fee payment|Year of fee payment: 5 |
    2020-12-23| PLFP| Fee payment|Year of fee payment: 6 |
    2021-12-24| PLFP| Fee payment|Year of fee payment: 7 |
    优先权:
    申请号 | 申请日 | 专利标题
    DE102014226986.5A|DE102014226986B9|2014-12-23|2014-12-23|Glass-ceramic substrate made of a transparent, colored LAS glass-ceramic and process for its production|
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