Glass-ceramic with specific thermal expansion behavior

Abstract

To provide a glass-ceramic with improved thermal expansion behavior and its use in a precision component.SOLUTION: There is provided a LAS glass-ceramic, which has a mean thermal expansion coefficient CTE in the range of 0 to 50°C of at most 0±0.02×10-6 / K and a thermal hysteresis of less than 0.1 ppm in the temperature range of 10°C to 35°C and which comprises the following components (in mol % based on oxide): SiO2 : 60 to 70, Li2O : 7 to 9.4, R2O (with R=Na, K, Cs, Rb): 0.7 to 2.0, MgO+ZnO : 0 to 0.4, at least one component selected from the group consisting of P2O5 and RO, where RO is CaO and / or BaO and / or SrO, and nucleating agents with a content of 1.5 to 6 mol %, where the nucleating agents are at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to glass ceramics having specific thermal expansion behavior and at the same time good melting, formability and ceramizability properties, as well as the use of the glass ceramics according to the invention in precision components.

[0002] Background of the Invention Materials and precision components with low thermal expansion or low CTE (Coefficient of Thermal Expansion) are already known in the prior art.

[0003] Ceramics, Ti-doped quartz glass, and glass ceramics are known as materials for precision components with low thermal expansion in the temperature range around room temperature. Glass ceramics with low thermal expansion are, in particular, lithium aluminum silicate glass ceramics (LAS glass ceramics), as described, for example, in U.S. Pat. Nos. 4,851,372, 5,591,682, EP 587979, 7,226,881, 7,645,714, DE 102004008824, and DE 102018111144. Another material for precision components is cordierite ceramic or cordierite glass ceramic.

[0004] Such materials are often used for precision components that must meet particularly stringent requirements regarding their properties (e.g., mechanical, physical, and optical properties). They are used, among other things, in ground- and space-based astronomy and Earth observation, LCD lithography, microlithography and EUV lithography, metrology, spectroscopy, and measurement technology. In this context, the components must have extremely low thermal expansion, depending on the specific application.

[0005] Generally, the thermal expansion of materials is measured by a static method, in which the length of a specimen is measured at the beginning and end of a specific temperature range, and the average coefficient of thermal expansion α or CTE (Coefficient of Thermal Expansion) is calculated from the difference in these lengths. In this case, the CTE is expressed as the average value for this temperature range, for example, CTE(0;50) or α(0;50) for the temperature range 0°C to 50°C.

[0006] To meet ever-increasing demands, materials have been developed with CTEs more tailored to the application of the components they will be made from. For example, the average CTE can be optimized not only for the standard temperature interval (CTE(0;50)) but also for a temperature interval near the actual application temperature, e.g., the 19°C to 25°C interval for a particular lithography application, i.e., CTE(19;25). In addition to determining the average CTE, the thermal expansion of the specimen can also be determined over a very small temperature interval and expressed as a CTE-T curve. Preferably, such a CTE-T curve has zero crossings at one or more temperatures, preferably at or near the intended application temperature. At the zero crossings of the CTE-T curve, the relative length change with temperature change is particularly small. In some glass ceramics, the zero crossings of such CTE-T curves can be shifted to the application temperature of the component by appropriate temperature treatment. To minimize the length change of the component when temperature changes only slightly, it is desirable to minimize the slope of the CTE-T curve near the application temperature, in addition to the absolute value of the CTE. The optimization of the CTE or thermal expansion mentioned above is usually done for these particular zero expansion glass-ceramics by varying the ceramization conditions at a constant composition.

[0007] One of the adverse effects in known precision components and materials, particularly glass ceramics such as LAS glass ceramics, is "thermal hysteresis," hereinafter abbreviated as "hysteresis." Hysteresis, as used herein, means that the change in length of a specimen when heated at a constant heating rate differs from the change in length of the specimen when subsequently cooled at a constant cooling rate, even if the absolute values ​​of the cooling rate and the heating rate are identical. A typical hysteresis loop is obtained by plotting the change in length as a function of the heating and cooling temperatures. The magnitude of the hysteresis loop also depends on the rate of temperature change. The faster the temperature change occurs, the more pronounced the hysteresis effect.

[0008] The hysteresis effect reveals that the thermal expansion of LAS glass ceramics depends on temperature and time, i.e., for example, on the rate of temperature change, and this is described in several specialist publications, e.g., O. Lindig and W. Pannhorst, “Thermal expansion and length stability of ZERODUR® in dependence on temperature and time”, APPLIED OPTICS, Vol. 24, No. 20, October 1985; R. Haug et al., “Length variation in ZERODUR® M in the temperature range from −60°C to +100°C”, APPLIED OPTICS, Vol. 28, No. 19, October 1989; R. Jedamzik ​​et al., “Modeling of the thermal expansion behavior of ZERODUR® at arbitrary temperature profiles”, Proc. SPIE Vol. 7739, 2010; D.B. Hall, “Dimensional stability tests over time and temperature for several low-expansion glass ceramics”, It is also mentioned occasionally in APPLIED OPTICS, Vol. 35, No. 10, April 1996.

[0009] Because the length change of glass ceramics exhibiting thermal hysteresis lags behind or precedes the temperature change, the material or its precision components exhibit a disturbing isothermal length change, i.e., after a temperature change, the material undergoes a length change even when the temperature is already held constant (so-called "isothermal hold"), and this continues until a steady state is reached. If the material is subsequently heated and cooled again, the same effect occurs again.

[0010] The temperature range of 0°C to 50°C, especially 10°C to 35°C or 19°C to 25°C, is often important for the properties of materials used in precision components, especially glass ceramics, where 22°C is commonly referred to as room temperature. Because many precision component applications occur in the temperature range from above 0°C to room temperature, materials with thermal hysteresis effects and isothermal length changes are disadvantageous because they can cause optical failures in optical components such as lithography mirrors and astronomy or space-based mirrors. This effect can lead to measurement errors in other precision components made of glass ceramics used in measurement technologies (e.g., precision scales, interferometer reference plates, etc.).

[0011] Some known materials, such as ceramics, Ti-doped fused silica, and certain glass-ceramics, have an average coefficient of thermal expansion (CTE) of 0±0.1×10 -6 / K (corresponding to 0±0.1 ppm / K) or lower. Materials with such low average CTEs in the temperature ranges mentioned are referred to as zero-expansion materials within the meaning of the present invention. However, glass ceramics, especially LAS glass ceramics with such optimized average CTEs, usually exhibit thermal hysteresis in the temperature range of 10°C to 35°C. This means that, especially in applications near room temperature (i.e., 22°C), these materials exhibit disruptive hysteresis effects, which impair the accuracy of precision components manufactured with such materials. For this reason, glass ceramic materials have been developed that do not exhibit significant hysteresis at room temperature (see U.S. Pat. No. 4,851,372). However, this effect is not eliminated, but merely shifted to lower temperatures, so that these glass ceramics exhibit significant hysteresis at temperatures below 10°C, which can also be disruptive. Therefore, to characterize the thermal hysteresis of a material in a specific temperature range, the thermal behavior of the material at different temperature points in this range is taken into account within the scope of the present invention. Furthermore, there are glass-ceramics that do not exhibit significant hysteresis at 22°C and 5°C, but these glass-ceramics have an average CTE(0;50) of >0±0.1 ppm / K, meaning that they are not zero-expansion glass-ceramics within the meaning of the above definition.

[0012] U.S. Patent Application Publication Nos. 2022 / 0298079, 2022 / 0298062, and WO 2022 / 194846 describe zero-expansion, hysteresis-free glass-ceramics. In the context of these applications, it is recognized that the MgO and ZnO components promote the development of thermal hysteresis, and therefore limiting the MgO and ZnO content is essential to provide a hysteresis-free LAS glass-ceramic at least in the temperature range of 10°C to 35°C.

[0013] For example, in EUV lithography applications it is desirable to further improve the expansion properties, especially to achieve a particularly flat CTE-T curve over a wide temperature range of 0-100°C.

[0014] Glass ceramics with particularly flat CTE-T curves or CTE plateaus are described in DE 10202811144 A1. According to this document, to achieve a CTE plateau, specific proportions and specific contents of both ZnO and MgO (total of at least 1.8 mol%) are required. However, these glass ceramics are not hysteresis-free.

[0015] It is also desirable for EUVL components to have good polishability and post-processability using ion beam figuring (IBF). To this end, it is advantageous to keep the BaO content in the glass-ceramic as low as possible.

[0016] Another requirement for glass-ceramic materials is the good meltability of the glass components as well as the simple melting control and homogenization of the glass melt, which is the basis for large-scale production facilities, so that - after ceramization of the glass - high demands on the glass-ceramic can be met with regard to uniformity of the CTE, internal quality - in particular low inclusions (especially bubbles), low striae levels - and polishability.

[0017] Therefore, one of the objectives of the present invention was to provide a glass-ceramic that is not only zero-expansion and hysteresis-free, but also has a flat CTE-T curve and good polishability, i.e., is primarily BaO-free.A further object was to provide a scalable glass-ceramic that has zero expansion and reduced thermal hysteresis, especially in the temperature range from 10°C to 35°C, and precision components manufactured from this material.

[0018] The above-mentioned problems are solved by the embodiments set forth in the claims.The present invention has various aspects.

[0019] According to one aspect of the present invention, there is provided an LAS glass ceramic, which has a maximum melting point of 0±0.02×10 in the range of 0 to 50°C. -6 / K and a thermal hysteresis of <0.1 ppm over the temperature range of at least 10°C to 35°C, and containing (in mole % on an oxide basis): SiO260~70 Li2O 7~9.4 R2O(R=Na, K, Cs, Rb) 0.7~2.0 MgO+ZnO 0~0.4 - at least one component selected from the group consisting of P2O5 and RO, where RO may be CaO and / or BaO and / or SrO, and - a nucleating agent having a content of 1.5 to 6 mol %, which is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, WO3;

[0010] A LAS glass-ceramic is provided, comprising:

[0020] According to a second aspect of the present invention, there is provided an LAS glass ceramic, the LAS glass ceramic having a melting point of 0±0.02×10 at most in the range of 0 to 50°C. -6 / K and a thermal hysteresis of <0.1 ppm over the temperature range of at least 10°C to 35°C, and containing (in mole % on an oxide basis): SiO260~70 Li2O 7~9.4 R2O(R=Na, K, Cs, Rb) 0.7~2.0 MgO+ZnO 0~0.4 BaO 0~<0.5 at least one component selected from the group consisting of P2O5 and RO, where RO may be CaO and / or SrO; and A nucleating agent having a content of 1.5 to 6 mol %, which is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3.

[0010] A LAS glass-ceramic is provided, comprising:

[0021] According to a third aspect of the present invention, there is provided an LAS glass ceramic, the LAS glass ceramic having a melting point of 0±0.02×10 at most in the range of 0 to 50°C. -6 / K and a thermal hysteresis of <0.1 ppm over the temperature range of at least 10°C to 35°C, and containing (in mole % on an oxide basis): SiO260~70 Li2O 7~9.4 K2O 0.7~2.0 Na2O 0~0.4 MgO+ZnO 0~0.4 at least one component selected from the group consisting of P2O5 and RO, where RO may be CaO and / or BaO and / or SrO; and A nucleating agent having a content of 1.5 to 6 mol %, which is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3.

[0010] A LAS glass-ceramic is provided, comprising:

[0022] According to a fourth aspect of the present invention, there is provided an LAS glass ceramic, the LAS glass ceramic having a melting point of 0±0.02×10 at most in the range of 0 to 50°C. -6 / K and a thermal hysteresis of <0.1 ppm over the temperature range of at least 10°C to 35°C, and containing (in mole % on an oxide basis): SiO260~70 Li2O 7~9.4 K2O 0.7~2.0 Na2O 0~0.4 MgO+ZnO 0~0.4 BaO 0~<0.5 at least one component selected from the group consisting of P2O5 and RO, where RO may be CaO and / or SrO; and A nucleating agent having a content of 1.5 to 6 mol %, which is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3.

[0010] A LAS glass-ceramic is provided, comprising:

[0023] According to another aspect, the invention relates to the use of such LAS glass ceramics as substrates for precision components.

[0024] According to a further aspect, the invention relates to the use of LAS glass ceramics in precision parts, in particular in metrology, spectroscopy, measuring technology, lithography, astronomy or Earth observation from outer space, e.g. as mirrors or mirror substrates for segmented or integrated astronomical telescopes, or also e.g. as lightweight or ultra-lightweight mirror substrates for space-based telescopes, or as high-precision structural elements for distance measurements, e.g. in space, or as optics for Earth observation, as standards for precision measurement technology, precision scales, reference plates in interferometers, mechanical precision parts, e.g. for ring laser gyroscopes, spiral springs in the watch industry, as mirrors and prisms, e.g. in LCD lithography, as mask holders, wafer stages, reference plates, reference frames and grid plates in microlithography and EUV (extreme UV) microlithography where reflective optics are used, and also for use as mirrors and / or photomask substrates or reticle mask blanks in EUV microlithography.

[0025] According to another aspect, the present invention relates to a precision component comprising an LAS glass ceramic. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 shows the CTE-T curve of the LAS glass ceramic according to Example 4. [Figure 2] 1 shows the CTE-T curve of the LAS glass ceramic according to Example 2. [Figure 3] 1 shows the CTE-T curve of the LAS glass ceramic according to Example 2. [Figure 4] FIG. 1 shows the CTE-T curve of the LAS glass ceramic according to Example 6. [Figure 5] FIG. 1 shows the hysteresis curve of the LAS glass ceramic according to Example 4. [Figure 6] FIG. 2 shows the CTE-T curve of the LAS glass ceramic according to Example 2. [Figure 7] FIG. 2 shows the normalized l / l0-T curve (also called dl / l0 curve) of a glass ceramic according to the invention (composition according to Example 4). [Figure 8] FIG. 2 shows the normalized l / l0-T curve (also called dl / l0 curve) of a glass ceramic according to the invention (composition according to Example 5). [Figure 9] FIG. 2 shows the normalized l / l0-T curve (also called dl / l0 curve) of a glass ceramic according to the invention (composition according to Example 3). [Figure 10] FIG. 2 shows the slope of the CTE-T curve from FIG. 1. [Figure 11] FIG. 3 shows the slope of the CTE-T curve from FIG. 2. [Figure 12] FIG. 5 shows the slope of the CTE-T curve from FIG. 4. [Figure 13] FIG. 10 shows the slope of the CTE-T curve from FIG. 9. [Figure 14] FIG. 1 shows the hysteresis curve of the LAS glass ceramic according to Example 23.

[0027] Detailed Description of the Invention The present invention provides a LAS glass-ceramic (hereinafter also referred to as glass-ceramic) which for the first time combines all relevant properties: - Average coefficient of thermal expansion (CTE) in the range of 0 to 50°C is 0±0.02×10 -6 / K, i.e., zero expansion. Furthermore, they exhibit a thermal hysteresis of <0.1 ppm, preferably <0.08 ppm, more preferably <0.05 ppm, at least in the temperature range from 10°C to 35°C. Materials with a low hysteresis effect of <0.1 ppm in the mentioned temperature range are hereinafter referred to as "hysteresis-free." As mentioned above, the magnitude of the hysteresis depends on the rate of temperature change used to determine it, so that statements about hysteresis in the context of the present invention relate to a heating / cooling rate of 36 K / h, i.e., 0.6 K / min. In advantageous embodiments, the LAS glass ceramic can be hysteresis-free in the temperature range from at least 5°C to 35°C or at least 5°C to 40°C, advantageously at least >0°C to 45°C, and according to certain embodiments even at least -5°C to 50°C. The glass-ceramics further exhibit a flat CTE-T curve or CTE plateau in the temperature range and contain no or only small amounts of BaO. - In addition, the glass melt is 10 3 The temperature at which it has a viscosity of 100 dPas, ie the temperature T3, is at most 1480°C, preferably at most 1460°C. - A variant of the invention is BaO-free and therefore suitable for IBF processing.

[0028] In particular, the properties of CTE, thermal hysteresis, and flat CTE-T curves or CTE plateaus are detailed below.

[0029] Glass ceramics are understood to be inorganic non-porous materials having a crystalline phase and a glassy phase, and typically the matrix, or continuous phase, is the glass phase. To produce glass ceramics, the components of the glass ceramic are first mixed, melted, and refined, resulting in the casting of a so-called green glass. After cooling, the green glass is reheated to crystallize in a controlled manner (so-called "controlled volume crystallization"). The analytical chemical composition of the green glass is identical to that of the glass ceramic produced therefrom; ceramization only changes the internal structure of the material. Therefore, when the composition of glass ceramics is discussed below, the same applies to the precursor of the glass ceramic, i.e., the green glass.

[0030] Until now, it has been thought that the glass components MgO and ZnO, either in combination or alone, are necessary to "flatten" the CTE-T curve of a material, particularly in zero-expansion LAS glass-ceramics, i.e., to reduce the slope of the CTE-T curve or CTE plateau in the temperature range. On the other hand, it has been found that the MgO and ZnO components can be present in only small proportions in a hysteresis-free LAS glass-ceramic. Therefore, there has been a contradiction: it is possible to either flatten the CTE-T curve of an LAS glass-ceramic or to make it hysteresis-free.

[0031] Within the scope of the present invention, LAS glass ceramics contain a crystalline phase exhibiting negative expansibility (which advantageously comprises or consists of a high-quartz solid solution, also known as β-eucryptite) and a glassy phase exhibiting positive expansibility. Besides SiO and AlO, LiO is the main component of the high-quartz solid solution. When present, ZnO and / or MgO are also incorporated into the high-quartz solid solution phase and, together with LiO, influence the expansion behavior of the crystalline phase. Thus, through the aforementioned provisions according to the present invention (reduction, preferably elimination, of MgO and ZnO), the type and properties of the high-quartz solid solution formed during ceramization can be significantly influenced. In the context of US Patent Application Publication Nos. 2022 / 0298079, 2022 / 0298062, and WO 2022 / 194846, MgO and ZnO were not used, but instead at least one component selected from the group consisting of PO, RO (RO can be NaO and / or KO and / or RbO and / or CsO), and RO (RO can be CaO and / or BaO and / or SrO) was used to adjust the desired expansion behavior of the glass-ceramic. Unlike MgO and ZnO, the mentioned alkaline earth metal oxides and alkali metal oxides, if present, remain in the glass phase and are not incorporated into the high-temperature quartz solid solution.

[0032] In an advantageous further development, the glass ceramic comprises the following components: Al2O310~22 P2O50.1~6 MgO 0~0.35 ZnO 0~0.4 R2O 0.7~2.0 RO 0.1~6 TiO2+ZrO21.5~6 may be included singly or in any combination in mole %.

[0033] In an advantageous further development, the glass ceramic comprises the following components: Al2O310~22 P2O50.1~6 MgO 0~0.3 ZnO 0~0.4 R2O 0.7~2.0 RO 0.1~6 TiO2+ZrO21.5~6 may be included singly or in any combination in mole %.

[0034] Furthermore, preferably, within the above-mentioned limits for R2O, RO and the sum of TiO2 + ZrO2, the following components: Na2O 0~<0.4 K2O 0.5~2.0 Cs2O 0~2 Rb2O 0~2 CaO 0.1~5 BaO 0~0.4 SrO 0-3 TiO20~5 ZrO20~3 may be contained alone or in any combination in mole % units.

[0035] In an advantageous embodiment, the LAS glass ceramic comprises (in mole % on an oxide basis): Al2O310~22 P2O50.1~6 MgO 0~0.35 ZnO 0~0.5 R2O 0.7~2.0 RO 0.1~6 Nucleating agent 1.5~6 Including, The nucleating agent is preferably TiO2 and / or ZrO2.

[0036] In an advantageous embodiment, the LAS glass ceramic comprises (in mole % on an oxide basis): Al2O310~22 P2O50.1~6 MgO 0~0.3 ZnO 0~0.4 R2O 0.7~2.0 RO 0.1~6 Nucleating agent 1.5~6 Including, The nucleating agent is preferably TiO2 and / or ZrO2.

[0037] In another advantageous embodiment, the LAS glass ceramic comprises (in mole % on an oxide basis): SiO260.50~69 Li2O 8~9.4 Al2O311~21 P2O50.5~6 MgO 0~0.2 ZnO 0~0.3 R2O 0.7~2.0 RO 0.2~4.5 Nucleating agent 2.5~5 Including, The nucleating agent is preferably TiO2 and / or ZrO2.

[0038] The glass ceramic contains at least 60 mol%, more preferably at least 60.5 mol%, even more preferably at least 61 mol%, even more preferably at least 61.5 mol%, and even more preferably at least 62.0 mol% of silicon dioxide (SiO2). The SiO2 content is at most 70 mol% or less, preferably at most 69 mol%, and also preferably at most 68.5 mol%. A high SiO2 content makes batch melting difficult and increases the viscosity of the melt, which can cause problems with melt homogenization in large-scale production facilities. Therefore, it is desirable not to exceed a content of 70 mol%. A high melt viscosity increases the melt processing temperature (Va). Very high temperatures are required for melt clarification and homogenization, which can lead to attack of the melting unit lining due to the aggressiveness of the melt, which increases with temperature. Furthermore, even high temperatures may not be sufficient to produce a homogeneous melt, which can result in striae and inclusions in the green glass (especially bubbles and particles originating from the lining of the melting unit), which, after ceramization, do not meet the requirements regarding the uniformity of the properties of the produced glass-ceramic, for example the requirements regarding the uniformity of the thermal expansion coefficient. For these reasons, an SiO content lower than the mentioned upper limit may be preferable.

[0039] The proportion of Al2O3 is advantageously at least 10 mol%, preferably at least 11 mol%, preferably at least 12 mol%, more preferably at least 13 mol%, also preferably at least 14 mol%, also preferably at least 14.5 mol%, and even more preferably at least 15 mol%. If the content is too low, a low-expansion solid solution is not formed, or if it is formed, it is formed too little. The proportion of Al2O3 is advantageously at most 22 mol%, preferably at most 21 mol%, preferably at most 20 mol%, even more preferably at most 19.0 mol%, and even more preferably at most 18.5 mol%. If the content of Al2O3 is too high, it leads to an increase in viscosity and promotes uncontrollable devitrification of the material.

[0040] According to one variant of the LAS glass-ceramic having an Al2O3 content of less than 17.0 mol%, for the CTE plateau, the following condition must be met: an Al2O3 content of at least 15.0 mol% or at least 15.8 mol% or at least 16.0 mol% or at least 16.1 mol% or more than 16.1 mol%, - an SiO2 content of at least 63.5 mol% or at least 63.75 mol% or at least 64.0 mol% and / or at most 65.6 mol% or at most 65.0 mol%, - 30.7 ≦ (molar SiO2 content - (2.0 × molar Al2O3 content)) or 30.9 ≦ (molar SiO2 content - (2.0 × molar Al2O3 content)) or 31.0 ≦ (molar SiO2 content - (2.0 × molar Al2O3 content)) applies, - (SiO2 molar content - (2.0 × Al2O3 molar content)) ≤ 34.0 applies It is advantageous to satisfy one or more of the following conditions.

[0041] According to another variant of the LAS glass-ceramic having an Al2O3 content of ≥ 17.0 mol%, for the CTE plateau the following conditions must be met: - an Al2O3 content of at most 19.5 mol% or at most 19.0 mol%, - an SiO2 content of at least 62.0 mol% or more than 62.0 mol% and / or up to 66.0 mol%; - 142.5 ≦ (molar SiO2 content + (4.6 × molar Al2O3 content)) or 143.0 ≦ (molar SiO2 content + (4.6 × molar Al2O3 content)) or 143.0 < (molar SiO2 content + (4.6 × molar Al2O3 content)) applies, - The following conditions: (SiO2 molar content + (4.6 × Al2O3 molar content)) ≤ 149.0, or (SiO2 molar content + (2.0 × Al2O3 molar content)) ≤ 101.0 or ≤ 100.5 One of the following applies: It is advantageous to satisfy one or more of the following conditions.

[0042] According to one variant, Al2O3 ≥ 17.0 mol% or ≤ 19.0 and 62.0 mol% - 66.0 mol% of SiO2 and The following applies: 142.5 ≦ (SiO2 molar content + (4.6 × Al2O3 molar content)) ≦ 149.0 applies.

[0043] Within the scope of the present invention, it has been found that for primarily ZnO- and MgO-free hysteresis-free glass-ceramics, the SiO2-Al2O3 ratio mentioned in DE 10202811144 A1 is desirable, but not sufficient. Surprisingly, it has been found that for hysteresis-free glass-ceramics that are desired to exhibit a CTE plateau, the alkali metal oxides Na2O and, in particular, K2O play an important role. According to DE 10202811144 A1, the total amount of sodium oxide (Na2O) and / or potassium oxide (K2O) is 0.1 to 0.7 mol %, and in other embodiments, can even be zero. However, for hysteresis-free glass-ceramics, the total content of R2O (R = Na, K, and / or Cs) must be maintained at >0.7 mol % in order to obtain a CTE plateau.

[0044] The glass ceramic according to the present invention can contain 0 to 6 mol% P2O5. The phosphate content of the glass ceramic P2O5 can be advantageously at least 0.1 mol%, preferably at least 0.3 mol%, preferably at least 0.5 mol%, also preferably at least 0.6 mol%, more preferably at least 0.7 mol%, and even more preferably at least 0.8 mol%. P2O5 is essentially incorporated into the crystalline phase of the glass ceramic, favorably influencing the crystalline phase and thus the expansion behavior of the glass ceramic. Furthermore, the melting of the components and the fining behavior of the melt are improved. However, if the P2O5 content is too high, the CTE-T curve in the temperature range from 0°C to 50°C will not exhibit the advantageously flat curve. Therefore, the P2O5 content in the glass ceramic is advantageously at most 6 mol%, preferably at most 5 mol%, more preferably at most 4 mol%, and even more preferably less than 4 mol%. According to individual embodiments, the glass ceramic may be P2O5-free.

[0045] Within the scope of the present invention, certain sums and ratios of SiO2, Al2O3 and / or P2O5 components, i.e., components that form high-temperature quartz solid solutions, may be useful for forming glass-ceramics according to the present invention.

[0046] The total proportion in mole percent of the basic components SiO2 + Al2O3 of the LAS glass ceramic is advantageously at least 75 mole percent, preferably at least 78 mole percent, preferably at least 79 mole percent, more preferably at least 80 mole percent, and / or preferably at most 90 mole percent, preferably at most 87 mole percent, preferably at most 86 mole percent, more preferably at most 85 mole percent. If this sum is too high, the viscosity curve of the melt will be shifted to higher temperatures, which is disadvantageous as already explained above for the SiO2 component. If this sum is too low, too little high-temperature quartz solid solution will be formed.

[0047] The total proportion in mol % of the basic components SiO2, Al2O3 and P2O5 of the LAS glass ceramic is preferably at least 77 mol %, advantageously at least 81 mol %, advantageously at least 83 mol %, more preferably at least 84 mol %, and / or preferably at most 91 mol %, advantageously at most 89 mol %, more preferably at most 87 mol %, and according to one variant at most 86 mol %.

[0048] The ratio of molar percentages of P2O5 to SiO2 is preferably at least 0.005, advantageously at least 0.01, preferably at least 0.012 and / or preferably at most 0.1, more preferably at most 0.08 and according to one variant at most 0.07.

[0049] As an additional component, the glass ceramic contains lithium oxide (LiO) in a proportion of at least 7 mol%, advantageously at least 7.5 mol%, preferably at least 8 mol%, and particularly preferably at least 8.25 mol%. The proportion of LiO is limited to a maximum of 9.4 mol%, more preferably at a maximum of 9.35 mol%, and even more preferably at a maximum of 9.3 mol% or less. LiO is a component of the high-temperature quartz solid solution phase and contributes significantly to the thermal expansion of the glass ceramic. It is desirable not to exceed the stated upper limit of 9.4 mol%, since otherwise a glass ceramic with a negative coefficient of thermal expansion (CTE) of (0:50) would result. If the LiO content is less than 7 mol%, the amount of high-temperature quartz solid solution formed is too small, and the CTE of the glass ceramic remains positive.

[0050] According to one variant of the glass-ceramic, the composition may satisfy the condition: molar SiO content + (5 × molar LiO content) ≥ 10 or preferably ≥ 10.5, preferably molar SiO content + (5 × molar LiO content) ≥ 10 or ≥ 10.5. Alternatively or additionally, advantageous upper limits of ≤ 115.5 or ≤ 114.5 or ≤ 113.5 may apply to the condition "molar SiO content + (5 × molar LiO content)".

[0051] The glass ceramic may contain at least one alkaline earth metal oxide selected from the group consisting of CaO, BaO, and SrO, collectively referred to as "RO." Components from the RO group remain substantially in the amorphous glass phase of the glass ceramic and may be important for maintaining the zero expansion of the ceramized material. If the sum of CaO + BaO + SrO is too high, the CTE (0:50) targeted by the present invention is not achieved. Therefore, the RO content is advantageously at most 6 mol% or at most 5.5 mol%, preferably at most 5 mol%, advantageously at most 4.5 mol%, preferably at most 4 mol%, preferably at most 3.8 mol%, even more preferably at most 3.5 mol%, and also preferably at most 3.2 mol%. If the glass ceramic contains RO, an advantageous lower limit can be at least 0.1 mol%, advantageously at least 0.2 mol%, preferably at least 0.3 mol%, and also preferably at least 0.4 mol%. According to individual embodiments, the glass ceramic may be free of RO.

[0052] According to one variant, the glass ceramic contains only a small proportion of BaO, at most <0.5 mol%, preferably at most 0.3 mol%, more preferably at most 0.1 mol%. Some variants of the glass ceramic do not contain BaO, i.e., they are BaO-free except for common impurities. If BaO is present, it may contain at least 0.1 mol% or at least 0.2 mol%. Surprisingly, even with small amounts or even without BaO, a good glass former, it is possible to produce LAS glass ceramics that exhibit good processing properties, in particular good polishability and post-processability by IBF.

[0053] CaO is a preferred RO component in the present invention, and the LAS glass-ceramic preferably contains at least 0.1 mol%, or at least 0.2 mol%, or at least 0.4 mol%, or at least 0.5 mol% CaO. The proportion of CaO may preferably be at most 5 mol%, advantageously at most 4 mol%, advantageously at most 3.5 mol%, advantageously at most 3 mol%, further preferably at most 2.8 mol%, more preferably at most 2.6 mol%.

[0054] The glass ceramic can contain at most 3 mol %, advantageously at most 2 mol %, preferably at most 1.5 mol %, preferably at most 1.3 mol %, preferably at most 1.1 mol %, more preferably at most 1 mol %, also preferably at most 0.9 mol %, and / or preferably at least 0.1 mol % SrO. According to individual embodiments, the glass ceramic is free of SrO except as impurities.

[0055] The glass ceramic may contain up to 0.4 mol % magnesium oxide (MgO). Further advantageous upper limits may be up to 0.2 mol %, up to 0.1 mol %, or up to 0.05 mol %. Particularly preferably, the glass ceramic according to the invention is free of MgO. The MgO component causes thermal hysteresis in the glass ceramic in the temperature range from 0°C to 50°C. The lower the MgO content in the glass ceramic, the smaller the hysteresis in the mentioned temperature range.

[0056] The glass ceramic may contain up to 0.4 mol % zinc oxide (ZnO). Further advantageous upper limits may be up to 0.2 mol %, up to 0.1 mol %, or up to 0.05 mol %. Particularly preferably, the glass ceramic according to the invention is free of ZnO. The ZnO component causes thermal hysteresis in the glass ceramic in the temperature range from 0°C to 50°C. The lower the ZnO content in the glass ceramic, the smaller the hysteresis in the mentioned temperature range.

[0057] Overall, MgO and ZnO are preferably contained in the hysteresis-free LAS glass-ceramic in relatively small proportions, in accordance with the invention, in a total proportion of at most 0.4 mol % or at most 0.3 mol % only. Preferred variants contain at most 0.2 mol %, at most 0.1 mol %, or at most 0.05 mol % or no MgO or ZnO.

[0058] Surprisingly, it has been found that, contrary to the teachings of the prior art, it is still possible to obtain LAS glass ceramics with flat CTE-T curves or CTE plateaus that are simultaneously zero-expansion and hysteresis-free. To this end, the proportion of alkali metal oxides in the LAS glass ceramic is set to 0.7 mol% to 2.0 mol%. Contents below 0.7 mol% or above 2.0 mol% lead to LAS glass ceramics that do not or do not have a sufficiently wide CTE plateau.

[0059] The total R2O content of sodium oxide (Na2O) and / or potassium oxide (KO) and / or cesium oxide (Cs2O) and / or rubidium oxide (Rb2O) is therefore at least 0.7 mol % and at most 2.0 mol %, or 1.9 mol %, or 1.8 mol %, and according to preferred variants at least 0.8 mol %, or at least 0.9 mol %, or at least 1.0 mol %. The Na2O, KO, Cs2O and Rb2O components remain essentially in the amorphous glass phase of the glass-ceramic and are important for maintaining the zero expansion of the ceramized material.

[0060] Na2O, KO, Cs2O, Rb2O may each, and independently of one another, be contained in the glass-ceramic in a proportion of at least 0.1 mol% or at least 0.2 mol% or at least 0.3 mol% or at least 0.4 mol% or at least 0.5 mol%, and / or at most 2.0 mol% or at most 1.5 mol% or at most 1.0 mol% or at most 0.5 mol% or at most 0.4 mol%.

[0061] According to a preferred variant, the LAS glass ceramic contains exclusively or mainly K2O as the alkali metal oxide. Surprisingly, it has been found that larger amounts of K2O can be incorporated into the LAS glass ceramic, i.e., at least 0.7 mol%, at least 0.8 mol%, at least 0.9 mol%, at least 1.0 mol%, at least 1.1 mol%, at least 1.2 mol%, or at least 1.3 mol%, without impairing the zero-expansion properties of the LAS glass ceramic. At the same time, the K2O content ensures a flat CTE-T curve. Furthermore, K2O reduces the temperature T3, thus ensuring better meltability and processability of the glass melt. According to this variant, Na2O is contained in a proportion of only at most 0.5 mol%, at most 0.2 mol%, or at most 0.1 mol%. The LAS glass ceramic can also be free of Na2O, except for common impurities, i.e., contain at most 0.05 mol% or 0.01 mol% Na2O.

[0062] The proportion of CsO can be at most 2 mol%, or at most 1.5 mol%, or at most 1 mol%, or at most 0.5 mol%, or at most 0.1 mol%, and the proportion of RbO can be at most 2 mol%, or at most 1.5 mol%, or at most 1 mol%, or at most 0.5 mol%, or at most 0.1 mol%.

[0063] According to a particular embodiment, the glass ceramic does not contain Na2O and / or Cs2O and / or Rb2O.

[0064] The glass ceramic further contains at least one nucleating agent selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3. The nucleating agent can be a combination of two or more of the mentioned components. Another advantageous nucleating agent is HfO2. Thus, in an advantageous embodiment, the glass ceramic comprises HfO2 and at least one nucleating agent selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3. The total proportion of nucleating agents is preferably at least 1.5 mol%, preferably at least 2 mol% or more than 2 mol%, more preferably at least 2.5 mol%, and according to one particular variant, at least 3 mol%. The upper limit can be at most 6 mol%, preferably at most 5 mol%, preferably at most 4.5 mol%, or at most 4 mol%. In particularly advantageous variants, the stated upper and lower limits apply to the sum of TiO2 and ZrO2.

[0065] The glass ceramic may contain titanium oxide (TiO) in a proportion of preferably at least 0.1 mol%, advantageously at least 0.5 mol%, preferably at least 1.0 mol%, preferably at least 1.5 mol%, preferably at least 1.8 mol%, and / or preferably at most 5 mol%, advantageously at most 4 mol%, more preferably at most 3 mol%, even more preferably at most 2.5 mol%, preferably 2.3 mol%. TiO-free variants of the glass ceramic according to the invention are possible.

[0066] The glass ceramic can advantageously further contain zirconium oxide (ZrO) in a proportion of at most 3 mol%, preferably at most 2.5 mol%, more preferably at most 2 mol%, preferably at most 1.5 mol%, or at most 1.2 mol%. Preferably, ZrO is contained in a proportion of at least 0.1 mol%, more preferably at least 0.5 mol%, at least 0.8 mol%, or at least 1.0 mol%. ZrO-free variants of the glass ceramic according to the invention are possible.

[0067] According to some advantageous variants of the invention, 0 to 5 mol % of Ta2O5 and / or Nb2O5 and / or SnO2 and / or MoO3 and / or WO3 can be contained in the glass ceramic alone or in total, for example, as an alternative or additional nucleation agent or to adjust optical properties, such as the refractive index. HfO2 can also be an alternative or additional nucleation agent. To adjust the optical properties, some advantageous variants can contain, for example, Gd2O3, YO3, HfO2, Bi2O3 and / or GeO2.

[0068] Glass ceramics are As2O3, Sb2O3, SnO2, SO4 2- , Cl - , Br - or mixtures thereof in a proportion of more than 0.05 mol % or at least 0.1 mol % and / or at most 1 mol %.

[0069] In order to provide the hysteresis-free and zero-expansion glass-ceramic according to the invention with the desired internal quality, in particular with a low bubble count and almost no striae, despite a reduced As2O3 content or even without As2O3, in an advantageous embodiment at least one chemical fining agent is used.

[0070] In an advantageous embodiment, the glass ceramic can contain, as chemical fining agent, at least one alternative redox fining agent and / or at least one evaporative fining agent and / or at least one decomposition fining agent instead of As2O3 or in addition to a small proportion of As2O3 (max 0.05 mol %). Since As2O3 is also a redox fining agent, redox fining agents used instead of or in addition to As2O3 are referred to within the scope of the present invention as "alternative redox fining agents".

[0071] In advantageous variants, the total content of detectable chemical fining agents in the glass ceramic (excluding the content of As2O3, if present in the glass ceramic) can be in the range of 0 mol% to 1 mol%. In advantageous embodiments, the total content of detectable fining agents in the glass ceramic (excluding As2O3) is greater than 0.01 mol%, preferably at least 0.05 mol%, preferably at least 0.1 mol%, preferably at least 0.15 mol%, advantageously at least 0.2 mol%, and / or at most 1 mol%, preferably at most 0.7 mol%, preferably at most 0.5 mol%, preferably at most 0.4 mol%. Some advantageous variants may contain at most 0.3 mol%, preferably at most 0.25 mol%, or at most 0.2 mol% of fining agents. The proportion of each component is detectable by analysis of the glass ceramic. This applies in particular to all fining agents described below, except for the sulfate components described.

[0072] Redox fining agents contain polyvalent or multivalent ions capable of adopting at least two oxidation states, which are in a temperature-dependent equilibrium with each other, thereby releasing gases, usually oxygen, at high temperatures. Therefore, certain polyvalent metal oxides can be used as redox fining agents. In an advantageous variant, the alternative redox fining agent can be at least one component selected from the group consisting of Sb2O3, SnO2, CeO2, MnO2, and Fe2O3. However, in principle, other redox compounds are also suitable, provided they release fining gases in the temperature range associated with fining and the transformation of the metal ion valence state into either a different oxide or metallic form. Many such compounds are described, for example, in DE-A-19939771. Alternative redox fining agents that release fining gases, especially oxygen, at temperatures below 1700°C, such as Sb2O3, SnO2, and CeO2, are preferred.

[0073] Through analysis of the glass-ceramic, the As2O3 content and / or the content of at least one alternative redox fining agent can be determined, allowing the expert to draw conclusions about the type and amount of fining agent used. The alternative redox fining agent can be added to the batch, for example, as an oxide.

[0074] In advantageous variants, the total content of alternative redox fining agents can be in the range of 0 mol% to 1 mol%. In advantageous embodiments, the total detectable content of alternative redox fining agents in the glass ceramic is greater than 0.01 mol%, preferably at least 0.05 mol%, preferably at least 0.1 mol%, preferably at least 0.15 mol%, advantageously at least 0.2 mol%, and / or at most 1 mol%, preferably at most 0.7 mol%, preferably at most 0.5 mol%, preferably at most 0.4 mol%. Some advantageous variants may contain at most 0.3 mol%, preferably at most 0.25 mol%, or at most 0.2 mol% of alternative redox fining agents.

[0075] The glass ceramic can contain 0 mol % to 1 mol % of antimony oxide (Sb2O3) as an alternative redox fining agent. In an advantageous embodiment, the glass ceramic contains more than 0.01 mol %, preferably at least 0.05 mol %, advantageously at least 0.1 mol %, advantageously at least 0.15 mol %, preferably at least 0.2 mol %, and / or preferably at most 1 mol %, advantageously at most 0.7 mol %, more preferably at most 0.5 mol %, even more preferably at most 0.4 mol %, preferably at most 0.3 mol % of Sb2O3. Since Sb2O3 is considered environmentally harmful, it can be advantageous to use as little Sb2O3 as possible for fining. The glass-ceramics of preferred embodiments are substantially SbO-free or Sb-free, where "substantially SbO-free" means that SbO is not intentionally added to the composition as a raw material component, but is present at most as an impurity, with the impurity limit in SbO-free glass-ceramics being a maximum of 0.01 mol %, preferably a maximum of 0.005 mol %. According to certain embodiments, the glass-ceramics are SbO-free.

[0076] The glass ceramic can contain 0 mol% to 1 mol% tin oxide (SnO2) as an alternative redox fining agent. In advantageous embodiments, the glass ceramic contains more than 0.01 mol% SnO2, preferably at least 0.05 mol%, advantageously at least 0.1 mol%, advantageously at least 0.15 mol%, preferably at least 0.2 mol%, preferably at least 0.3 mol%, and / or preferably at most 1 mol%, advantageously at most 0.7 mol%, and more preferably at most 0.6 mol%. In some variants, an upper limit of at most 0.5 mol%, even more preferably at most 0.4 mol%, preferably at most 0.3 mol% can be advantageous. If the SnO2 content is too high, it may be difficult to control the ceramization process of the green glass, since a high SnO2 content acts not only as a fining agent but also as a crystal nucleation agent. SnO2-free or Sn-free variants of the glass-ceramics according to the invention are possible and advantageous, i.e. no Sn-containing raw materials were added to the batch for fining the basic green glass, and the impurity limit for SnO2 introduced by the raw materials or process was max. 0.01 mol %, preferably max. 0.005 mol %.

[0077] The glass-ceramic may contain 0 mol % to 1 mol % of CeO2 and / or MnO2 and / or Fe2O3 as alternative redox fining agents, each and independently of the other, preferably in a proportion of more than 0.01 mol %, preferably at least 0.05 mol %, advantageously at least 0.1 mol %, advantageously at least 0.15 mol %, preferably at least 0.2 mol %, and / or preferably at most 1 mol %, advantageously at most 0.7 mol %, more preferably at most 0.5 mol %, even more preferably at most 0.4 mol %, preferably at most 0.3 mol %. A preferred variant of the glass-ceramic is free of CeO2 and / or MnO2 and / or Fe2O3, i.e. no Ce-containing raw materials and / or Mn-containing raw materials and / or Fe-containing raw materials were added to the batch for fining the basic green glass, and the impurity limits for CeO2 and / or MnO2 and / or Fe2O3 introduced by the raw materials or process were max. 0.01 mol %, preferably max. 0.005 mol %.

[0078] Evaporative fining agents are components that volatilize at high temperatures due to vapor pressure, so that the gas formed in the melt exerts a fining effect.

[0079] In an advantageous variant, the evaporative fining agent can contain a halogen component.

[0080] In an advantageous variant, the evaporative fining agent can contain at least one halogen with a fining effect, in particular a halogen selected from the group consisting of chlorine (Cl), bromine (Br), and iodine (I). A preferred halogen with a fining effect is chlorine. Fluorine is not a halogen with a fining effect because it is already volatile at too low a temperature. Nevertheless, the glass ceramic can contain fluorine. However, fluorine can reduce the transparency of the glass ceramic, so this component, if present, is preferably limited to a maximum of 0.5 mol%, preferably a maximum of 0.3 mol%, and preferably a maximum of 0.1 mol%. Preferably, the glass ceramic is fluorine-free.

[0081] The fining halogen can be added in various forms. In one embodiment, it is added to the batch as a salt with an alkali metal or alkaline earth metal cation, or as an aluminum halogen. In one embodiment, the halogen is used as a salt, and the cation in the salt corresponds to the cation present as an oxide in the glass ceramic. The fining halogen can be used in the form of a halide compound, particularly a halide compound. Suitable halide compounds are, in particular, salts of chloride, bromide, and / or iodide anions with alkali metal, alkaline earth metal, or aluminum cations. Preferred examples are chlorides such as LiCl, NaCl, KCl, CaCl2, BaCl2, SrCl2, and AlCl3, and combinations thereof. Corresponding bromides and iodides such as LiBr, LiI, NaBr, NaI, KBr, KI, CaI2, and CaBr2, and combinations thereof, are also possible. Other examples are BaBr2, BaI2, SrBr2, SrI2, and combinations thereof.

[0082] In advantageous variants, the total content of halogens with a fining effect (i.e., Cl and / or Br and / or I) can be in the range of 0 mol% to 1 mol%. In advantageous embodiments, the total content of halogens with a detectable fining effect in the glass ceramic is greater than 0.03 mol%, preferably at least 0.04 mol%, preferably at least 0.06 mol%, preferably at least 0.08 mol%, preferably at least 0.1 mol%, preferably at least 0.15 mol%, advantageously at least 0.2 mol%, and / or at most 1 mol%, preferably at most 0.7 mol%, preferably at most 0.5 mol%, preferably at most 0.4 mol%. Some advantageous variants can also contain halogens with a fining effect in an amount of at most 0.3 mol%, preferably at most 0.25 mol%, or at most 0.2 mol%. The stated content refers to the amount of halogen detectable in the glass ceramic. Experts generally calculate the amount of halogen or halogen compounds required for fining based on these specifications.

[0083] The glass ceramic can contain 0 mol% to 1 mol% chlorine (atomically defined and designated as Cl). In advantageous embodiments, the glass ceramic contains more than 0.03 mol% Cl, advantageously at least 0.04 mol%, advantageously at least 0.05 mol%, advantageously at least 0.1 mol%, advantageously at least 0.15 mol%, preferably at least 0.2 mol%, and / or preferably at most 1 mol%, advantageously at most 0.7 mol%, more preferably at most 0.5 mol%, even more preferably at most 0.4 mol%, preferably at most 0.3 mol%. Some advantageous glass ceramics may be Cl-free, i.e., no Cl-containing raw materials were added to the batch for fining the base green glass. Cl is present at most as an impurity, with a Cl impurity limit of at most 0.03 mol%.

[0084] The same ranges and limitations as mentioned for Br as a halogen having a fining effect apply. The same ranges and limitations as mentioned for I as a halogen having a fining effect apply. A preferred variant of the glass-ceramic does not contain Br and / or I.

[0085] Instead of, or in addition to, evaporative fining agents and / or alternative redox fining agents, chemical fining agents can contain at least one decomposition fining agent. Decomposition fining agents decompose at high temperatures to release fining gases, and the decomposition products are released at sufficiently high gas pressures, especially at temperatures above 10 5 The decomposition fining agent is an inorganic compound having a gas pressure greater than 10 Pa. Preferably, the decomposition fining agent is a salt containing an oxoanion, particularly a sulfate component. Preferably, the decomposition fining agent contains a sulfate component. Through the decomposition of the component added as sulfate, SO2 and O2 gases are released at high temperatures, which contribute to the fining of the melt.

[0086] The sulfate component can be added in various forms. In one embodiment, it is added to the batch as a salt with an alkali metal or alkaline earth metal cation. In one embodiment, the sulfate is used as a salt, and the cation in the salt corresponds to the cation present as an oxide in the glass-ceramic. For example, the following components can be advantageously used as sulfate sources: LiSO, NaSO, KSO, CaSO, BaSO, SrSO.

[0087] Within the scope of the present invention, sulfate is determined as SO3 in the material analysis. However, since LAS glass-ceramics have a very low solubility for sulfate, the sulfate component (i.e., SO3) in the melt product after melting is no longer detectable by conventional X-ray fluorescence analysis. Therefore, in the case of sulfate-fined embodiments (see below), SO4 is determined in connection with the synthesis of the glass melt. 2- Or the mole percent of SO3 used is specified. Whether a sulfate component was used as a fining agent can be determined, for example, by analyzing the residual gas content (SO2) in the glass ceramic.

[0088] The preferred sulfate-fined glass ceramics have been doped with more than 0.01 mol %, preferably at least 0.05 mol %, advantageously at least 0.1 mol %, advantageously at least 0.15 mol %, preferably at least 0.2 mol %, and / or preferably at most 1 mol %, advantageously at most 0.7 mol %, more preferably at most 0.5 mol %, even more preferably at most 0.4 mol %, preferably at most 0.3 mol % SO3 during synthesis via at least one corresponding sulfate compound. 2- Therefore, the proportion of fining-effective sulfate added in the synthesis of the glass-ceramic can range from 0 mol % to 1 mol % SO3.

[0089] According to a variant of the invention, suitable metal sulfides can be used as decomposition fining agents to refine glass ceramics or base glasses, as described, for example, in US 2011 / 0098171. In one embodiment, the cations in the sulfides correspond to the cations present as oxides in the glass ceramic. Examples of suitable metal sulfides are alkali metal sulfides, alkaline earth metal sulfides, and / or aluminum sulfides, which release SO3 into the melt under oxidizing conditions. In order for metal sulfides to fully function as fining agents, they are advantageously used in combination with an oxidizing agent, preferably a nitrate and / or a sulfate.

[0090] Advantageous glass-ceramics with reduced As2O3 content or advantageous As2O3-free glass-ceramics can have a combination of chemical fining agents. The following combinations can be advantageous, each glass-ceramic preferably containing the mentioned fining agents individually and / or in total within the above-mentioned limits. Advantageous embodiments are: - SnO2 and / or Sb2O3, each with a maximum of 0.05 mol% As2O3; or - As2O3-free combinations, e.g.: Sb2O3 and SnO2; Sb2O3 and Cl, Sb2O3 and SO3; or - As2O3-free and Sb2O3-free combinations, e.g.: SnO2 and Cl, SnO2 and SO3, Cl and SO3 Includes.

[0091] Alternatively, glass-ceramics refined with only one fining agent may also be advantageous, for example glass-ceramics containing only Sb2O3 or only SnO2 as fining agent.

[0092] The fining of a melt using the above-mentioned chemical fining agents is based on the principle of adding a compound that decomposes and releases a gas, a compound that volatilizes at high temperatures, or a compound that releases a gas in an equilibrium reaction at high temperatures. However, instead of or in addition to this fining, known physical fining processes, such as reducing the viscosity of the glass melt by increasing the temperature, vacuum fining, and high-pressure fining, can also be advantageously used.

[0093] In an advantageous variant of the invention, the batch can contain nitrates (NO3), which act as oxidizing agents in the melting and fining process, ensuring the existence of oxidizing conditions in the melt and enhancing the effectiveness of the fining agents used, especially alternative redox fining agents. In one embodiment, the nitrates are used as salts, and the cations in the salts correspond to the cations present as oxides in the glass-ceramic. Examples of such salts are aluminum nitrate, alkali metal nitrates, alkaline earth metal nitrates, and zirconium nitrate. However, ammonium nitrate can also advantageously serve as a nitrate source. A nitrate compound or a mixture of nitrate compounds can be used. When a nitrate compound or a mixture of nitrate compounds is contained in the batch to assist the fining process, NO3 -The sum of is preferably at least 0.4 mol%, preferably at least 0.5 mol%, preferably at least 0.8 mol%, preferably at least 1 mol%, and / or advantageously at most 5 mol%, preferably at most 4 mol%. In some advantageous variants, up to 3 mol% of nitrate can also be used. Due to their volatility, nitrate cannot be detected in the glass or glass ceramic.

[0094] The glass compositions described above may contain coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, CuO, CeO2, Cr2O3, and rare earth oxides, either singly or in a total content of 0 to 3 mol %. A preferred variant does not contain any coloring oxides.

[0095] B2O3 can have a negative effect on the transparency of the glass-ceramic. Therefore, the content of this component is limited in preferred variants to <0.2 mol %, preferably to a maximum of 0.1 mol %. Preferred variants are B2O3-free.

[0096] The LAS glass ceramic is preferably fluorine-free. Fluorine can reduce the transparency of the glass ceramic and adversely affect its zero expansion properties. This component, if desired, is preferably limited to a maximum of 0.5 mol %, preferably a maximum of 0.3 mol %, preferably a maximum of 0.1 mol %. Preferably, the glass ceramic is fluorine-free.

[0097] According to an advantageous embodiment of the invention, the composition does not contain any other ingredients than those mentioned above.

[0098] According to an advantageous embodiment of the invention, the glass ceramic or green glass according to the invention preferably consists of at least 90 mol %, more preferably at least 95 mol %, most preferably at least 99 mol % of the above-mentioned components, or preferably the components SiO, AlO, LiO, PO, RO, RO, and a nucleating agent.

[0099] According to an advantageous further development of the glass ceramic, it is substantially free of one or more glass components selected from the group consisting of PbO, CrO3 and Cd compounds.

[0100] According to the present invention, the expressions "X-free" or "not containing component X" mean that the glass-ceramic is essentially free of component X, i.e., such component is present in the glass at most as an impurity and is not added to the composition as a single component. With regard to impurities, particularly MgO and / or ZnO, it is desirable for MgO-free and / or ZnO-free variants not to exceed the limit of 0.03 mol %, preferably 0.01 mol %, of each single component. For other glass components, higher impurity contents of up to 0.1 mol %, preferably up to 0.05 mol %, advantageously up to 0.01 mol %, advantageously up to 0.005 mol %, are possible, and for some components, advantageously up to 0.003 mol %, of each component, are possible. Here, X represents an optional component, such as PbO.

[0101] The glass ceramic according to the present invention has a high-temperature quartz solid solution as the predominant crystalline phase. The predominant crystalline phase is the crystalline phase that occupies the largest volume percent of the crystalline phase. The high-temperature quartz solid solution is a metastable phase that changes composition and / or structure or transforms into another crystalline phase depending on the crystallization conditions. The high-temperature quartz solid solution crystals exhibit very low or even decreasing thermal expansion as the temperature increases. In an advantageous embodiment, the crystalline phase does not contain β-spodumene or keatite.

[0102] Advantageous embodiments of the LAS glass ceramic have a crystalline phase content of less than 70% by volume and / or advantageously more than 45% by volume. The crystalline phase consists of high-temperature quartz solid solution, also known as β-eucryptite. The average crystallite size of the high-temperature quartz solid solution is advantageously <100 nm, preferably <80 nm, preferably <70 nm. The small crystallite size makes the glass ceramic transparent and also improves polishability. In one particularly advantageous variant, the average crystallite size of the high-temperature quartz solid solution can be ≦60 nm, preferably ≦50 nm. The crystalline phases, their proportions and the average crystallite size are determined in a known manner by X-ray diffraction analysis.

[0103] According to one embodiment of the present invention, transparent glass ceramics are produced. This transparency allows for better evaluation of many of the properties of such glass ceramics, particularly their internal quality. The glass ceramics according to the present invention are transparent, i.e., they have a net transmittance of at least 70% in the wavelength range from 350 to 650 nm. B2O3 and / or a higher fluorine content can decrease transparency. Therefore, advantageous variants do not contain one or both of the mentioned components. Furthermore, the glass ceramics produced within the scope of the present invention are pore-free and crack-free. Within the scope of the present invention, "pore-free" means a porosity of less than 1%, preferably less than 0.5%, and more preferably less than 0.1%. Cracks are gaps, i.e., discontinuities, in an otherwise continuous structure.

[0104] To produce homogeneous glass ceramics in large-scale production facilities, the processing temperature Va of the green glass (and thus the glass ceramic) on which the glass ceramic is based is advantageously at most 1330° C., preferably at most 1320° C. Some advantageous variants may have a processing temperature of at most 1310° C. or at most 1300° C. or below 1300° C. or below 1280° C. or below 1270° C. The processing temperature Va is determined by the temperature at which the melt is heated to 100° C. 4 This is the temperature at which the melt has a viscosity of 10 dPas, and is therefore also called temperature T4. 3The temperature at which the viscosity is 100 dPas is referred to as temperature T3. Preferably, this temperature T3 is at most 1480°C, or at most 1460°C, or at most 1450°C, or at most 1440°C, or at most 1435°C. Homogeneity refers in particular to the uniformity of the CTE of the glass ceramic over a large volume, and the low presence, preferably the absence, of inclusions such as bubbles and particles. This is a quality characteristic of glass ceramics and a prerequisite for use in precision components, especially very large precision components.

[0105] The processing temperature is determined by the composition of the glass ceramic. In particular, the glass network former SiO2 is considered to be the component that has a decisive influence on the viscosity and thus the increase in processing temperature, so the maximum SiO2 content should be selected according to the above specifications.

[0106] Coefficient of Thermal Expansion (CTE) The glass ceramic according to the invention has zero expansion, i.e., a maximum of 0±0.02×10 in the range of 0 to 50°C. -6 / K. Some advantageous variations have an average coefficient of thermal expansion (CTE) of at most 0±0.01×10 in the range of 0 to 50°C. -6 In certain applications, the average CTE may even be at most 0±0.02×10 / K over a wider temperature range, e.g., from −30° C. to +70° C., preferably from −40° C. to +80° C. -6 It may be advantageous to have / K, i.e., zero expansion.

[0107] To determine the CTE-T curves of the glass ceramic and precision component according to the present invention and the comparative examples, the differential CTE (T) is first determined. The differential CTE (T) is determined as a function of temperature. The CTE is then determined according to the following equation (1): CTE(T)=(1 / l0)×(∂l / ∂T) (1)

[0108] To generate a l / l0-T curve or strain curve or a plot of the change in length l / l0 of a test piece (glass ceramic or precision part) versus temperature, the initial length l0 at initial temperature t0 is changed to the length l at temperature t. t The temperature-dependent length change of a specimen can be measured up to 100°C. Preferably, a small temperature interval, such as 5°C, 3°C, or 1°C, is selected to determine the measurement points. Such measurements can be performed, for example, by dilatometry, interferometry, e.g., the Fabry-Perot method, i.e., evaluating the shift of the resonance peak of a laser beam incident on the material, or other suitable methods. Within the scope of the present invention, the dilatometry method was selected for a bar-shaped specimen of 100 mm in length and 6 mm in diameter in a temperature interval of 1°C to determine the CTE. The method selected for determining the CTE preferably has an accuracy of at least ±0.05 ppm / K, preferably at least ±0.03 ppm / K. However, the CTE can, of course, also be determined by a method with an accuracy of at least ±0.01 ppm / K, preferably at least ±0.005 ppm / K, or, according to some embodiments, even at least ±0.003 ppm / K or at least ±0.001 ppm / K.

[0109] From the l / l0-T curve, the average CTE for a specific temperature interval, for example, the temperature range of 0°C to 50°C, is calculated.

[0110] The CTE-T curve is obtained by deriving the l / l0-T curve. From the CTE-T curve, the zero crossings and the slope of the CTE-T curve within a temperature interval can be determined. From the CTE-T curve, the shape and location of the advantageous CTE "plateau" formed in some variants can be determined (see below and e.g., Figures 1 and 2).

[0111] An advantageous embodiment of a precision component comprising the glass ceramic according to the invention (especially in the form of a substrate) has a high CTE uniformity. The value of the CTE uniformity (English: "total spatial variation of CTE") is understood to be the so-called peak-to-valley value, i.e. the difference between the highest and lowest CTE values ​​of samples taken from the precision component. CTE uniformity therefore does not refer to the CTE of the component material, but rather to the spatial variation of the CTE over the considered area or the entire precision component. To determine the CTE uniformity, a number of samples are taken from the precision component at different positions and a CTE value is determined for each, which is expressed in ppb / K, where 1 ppb / K=0.001×10 -6 / K. The CTE uniformity, i.e., the spatial variation of the CTE, across the precision component is advantageously at most 5 ppb / K, preferably at most 4 ppb / K, and most preferably at most 3 ppb / K. Methods for determining CTE uniformity and means for achieving CTE uniformity are described in WO 2015 / 124710, the disclosure of which is incorporated herein by reference in its entirety.

[0112] Thermal Hysteresis Within the scope of the present invention, glass ceramics exhibit a thermal hysteresis of <0.1 ppm at least in the temperature range from 10°C to 35°C and are therefore already considered hysteresis-free (see Figures 5 and 6). Thus, at any temperature within the temperature interval from 10°C to 35°C, the glass ceramic, after being subjected to a temperature change, exhibits an isothermal length change in the positive or negative direction of less than 0.1 ppm at subsequent constant temperatures, i.e., <|0.1 ppm| or <±0.1 ppm. Preferably, LAS glass ceramics exhibit a thermal hysteresis of <|0.08 ppm| or <|0.05 ppm| at least in the temperature range from 10°C to 35°C.

[0113] In an advantageous embodiment, this hysteresis-free behavior exists over a temperature range of at least 5 to 35°C, preferably at least 5 to 45°C, preferably at least >0°C to 45°C, preferably at least -5°C to 50°C. Particularly preferred is a wider temperature range for the hysteresis-free behavior, so that the material or component is also suitable for applications at temperatures up to at least 100°C, advantageously even above that. Particularly preferred is a wider temperature range for the hysteresis-free behavior. Preferred application temperatures are in the range of -60 to 100°C, more preferably -40 to +80°C. Special variants of the invention relate to glass ceramics and precision components for application temperatures TA in the range of, for example, 5°C to 20°C, or TAs of 22°C, 40°C, 60°C, 80°C, and 100°C, which preferably also exhibit hysteresis-free behavior at these temperatures.

[0114] The thermal hysteresis was determined for the glass ceramics and precision components according to the invention, as well as for comparative examples, on rod-shaped specimens (i.e., precision component specimens or glass ceramic specimens) with a length of 100 mm and a diameter of 6 mm using a precision dilatometer capable of determining the CTE with a reproducibility of ±0.001 ppm / K and ±0.003 ppm / K (absolute value) in a temperature range of 1°C, according to the method and apparatus configuration disclosed in DE 10 2015 113 548 A1, the disclosure of which is incorporated herein in its entirety. For each specimen examined, the length change l / l0 was determined as a function of temperature while cooling from 50°C to -10°C at a cooling rate of 36 K / h. After an isothermal hold time of 5 hours at -10°C, the specimens were heated to 50°C at a heating rate of 36 K / h, and the length change l / l0 was recorded as a function of temperature. The thermal hysteresis behavior of the specimens is considered at -5°C, 0°C, 5°C, 10°C, 22°C, 35°C, and 40°C. These points are representative of the temperature range from -10°C to 50°C, since in the mentioned temperature interval the hysteresis decreases with increasing temperature. Thus, a specimen that is hysteresis-free at 22°C or 35°C will also not show hysteresis in the range up to 50°C.

[0115] To determine the thermal hysteresis at 10°C, individual measurements of the length change were recorded at five temperatures: 8°C, 9°C, 10°C, 11°C, and 12°C, i.e., two temperature points above and below 10°C, while the sample was both heated and cooled between -10°C and 50°C at a rate of 36 K / h. The average value was calculated from the difference between the measurements of the heating and cooling curves for these five measurement points, and this was reported in the tables as "Hyst.@10°C" in [ppm].

[0116] To determine the thermal hysteresis at 35°C, individual measurements of the length change were recorded at five temperatures: 33°C, 34°C, 35°C, 36°C, and 37°C, i.e., two temperature points above and below 35°C, while the sample was both heated and cooled between -10°C and 50°C at a rate of 36 K / h. The average value was calculated from the difference in measurements of the heating and cooling curves at these five measurement points, and this was reported in the table as "Hyst.@35°C" in [ppm].

[0117] A similar procedure was followed for the other temperature points mentioned above.

[0118] 3, 4, and 14 show thermal hysteresis curves for glass-ceramics according to the invention. The cooling curve (dashed line) and heating curve (dotted line) overlap at least in the temperature range of 10°C to 35°C, i.e., the glass-ceramic is hysteresis-free. However, the material is hysteresis-free not only in the range of 10°C to 35°C, but also in the range of at least 5°C to 35°C or 5°C to 45°C, preferably at least in the range of >0°C to 45°C.

[0119] Further expansion properties Advantageous embodiments of the present invention exhibit additional advantageous expansion characteristics.

[0120] To describe the expansion behavior of a test specimen (glass ceramic or precision component), the TCL value is often given, where TCL stands for "Total Change of Length." Within the scope of the present invention, the TCL value is given in the temperature range of 0°C to 50°C, in the temperature range of 0°C to 80°C, or in the temperature range of 0°C to 100°C. It is determined from the normalized l / l0-T curve (also referred to as Δl / l0-T curve in the figures) of each test specimen, where "normalized" means that the length change at 0°C is 0 ppm. The l / l0-T curve for TCL determination is generated using the same method as described above for CTE determination within the scope of the present invention.

[0121] The TCL value is the difference between the highest and lowest dl / l0 values ​​in this temperature range (here 0°C to 50°C): TCL(0;50℃)=|dl / l0max.|+|dl / l0min.| (2) where "dl" represents the change in length at each temperature, and "l0" represents the length of the specimen at 0°C. The calculation is based on the absolute value of the dl / l0 value.

[0122] Figures 7-9 show expansion curves of known materials, from which the maximum and minimum dl / l0 values ​​for calculating the TCL value can be read (see also below). Each expansion curve shows a curved progression over the temperature range 0°C to 50°C.

[0123] However, in the context of the present invention, a flat progression of the expansion curve in the temperature range 0° C. to 50° C. is an advantageous feature of glass ceramics and precision components (see FIGS. 12 and 13). In some advantageous variants, depending on the field of application of the component, a flat progression of the expansion curve may also be desirable in different temperature ranges, in particular in the ranges (0;80), (0;100), (20;40), (20;70) and / or (−10;30).

[0124] Preferably, the TCL over a selected temperature range, for example, a temperature range of 0°C to 50°C, is at most 1.00 ppm, or at most 0.50 ppm, or at most 0.01 ppm.

[0125] As an expression of the degree to which the course of the thermal expansion curve deviates from a simple linear course, in an advantageous embodiment of the invention a parameter F is introduced as an index of the flatness of the expansion curve, which allows the classification of CTE curves: F = TCL(0;50℃) / |Expansion(0;50℃)| (3)

[0126] The parameter F is calculated by dividing the TCL(0;50) value (in ppm) (see above) by the difference in expansion (in ppm) between the temperature points 0°C and 50°C. Since the expansion curves for TCL determination are, by definition, normalized so that the length change at 0°C is 0 ppm, the "difference in expansion between the temperature points 0°C and 50°C" corresponds to the "expansion at 50°C" shown in the table. The absolute value of the expansion at 50°C is used to calculate the parameter F.

[0127] For each material or component, it is advantageous if the parameter F is <1.10 or <1.05 or <1.03. The closer the parameter F is to 1, the flatter the progression of the expansion curve.

[0128] Thus, advantageous glass ceramics and precision components of the present invention not only exhibit a very flat expansion curve, for example in the temperature range from 0°C to 50°C, i.e., they are zero-expansion in the considered temperature range, but also exhibit a small variation in the change in length expansion, and thus in the change in differential CTE, in this range. As can be seen in Figure 9, advantageous embodiments of the present invention also exhibit a flat expansion curve over an even wider temperature range (here, for example, from 0°C to 65°C). The expansion behavior can also be considered in other selected temperature ranges, in particular (0;80), (0;100), (-10;30), (20;40), and (20;70), as will be described below.

[0129] Glass ceramics with a flat expansion curve are highly advantageous because precision components can be optimized for later application temperatures and also exhibit low thermal expansion, for example, at higher and / or lower temperature loads during production. Precision components for microlithography, EUV microlithography (also referred to as "EUV lithography" or "EUVL"), and metrology are typically used in standard cleanroom conditions, particularly at room temperature of 22°C. The CTE can be adapted to the application temperature. However, such components are subjected to various process steps, such as coating with metal layers, cleaning, structuring, and / or exposure processes, during which temperatures higher or possibly lower than those prevailing during later use in the cleanroom may be present. Therefore, advantageous glass ceramics and precision components made therefrom that have a parameter F of <1.10 and therefore exhibit optimized zero expansion not only at application temperatures but also, potentially, at higher and / or lower temperatures during production. Properties such as freedom from hysteresis and a parameter F<1.10 are particularly advantageous when the precision component or glass ceramic is used in EUV lithography, i.e., for example, when the precision component is an EUVL mirror or EUVL mask blank or the corresponding substrate, since in EUV lithography, the mirror or mask in particular is heated very non-uniformly in the point or beam direction by the irradiation with high-energy radiation. Under these operating conditions, it is advantageous for the precision component or glass ceramic to have a small slope of the CTE-T curve in the temperature range around the application temperature (see below).

[0130] Advantageous glass ceramics and precision components that are even better optimized for application temperatures of 20 or 22°C at a later time point are characterized by a relative length change (dl / l0) in the temperature range from 20°C to 30°C of ≦|0.10| ppm, preferably ≦|0.09| ppm, particularly preferably ≦|0.08| ppm, and very particularly preferably ≦|0.07| ppm and / or a relative length change (dl / l0) in the temperature range from 20°C to 35°C of ≦|0.17| ppm, preferably ≦|0.15| ppm, particularly preferably ≦|0.13| ppm, and very particularly preferably ≦|0.11| ppm. Alternatively or additionally, the glass ceramics and precision components thus optimized can be characterized by a relative length change (dl / l0) of ≦|0.30| ppm, preferably ≦|0.25| ppm, particularly preferably ≦|0.20| ppm, and especially preferably ≦|0.15| ppm in the temperature range from 20° C. to 40° C. The relative length change characteristics for the different temperature intervals can preferably be read from the dl / l0 curves in FIGS. 7 to 9. When referring to the relative length change (dl / l0), this specification naturally refers to the absolute value of the respective value.

[0131] Zero-expansion, hysteresis-free materials with such advantageous expansion behavior are particularly suitable for use as substrates for EUVL mirrors, or as EUVL mirrors that are heated to different degrees in light and shadow areas during operation, for example, due to the respective exposure mask. Due to the small relative length changes described above, EUVL mirrors formed from advantageous glass-ceramics exhibit smaller local gradients (local slopes or local tilts) in the topography of the mirror surface than EUVL mirrors made from known materials. The same applies analogously to EUVL mask blanks, EUVL masks, or EUVL photomasks.

[0132] In particular, in the case of glass-ceramics that exhibit a very flat course of the expansion curve in the temperature range under consideration, which fluctuates close to or around 0 ppm—which is an overall advantageous expansion behavior—it may be advantageous to introduce another measure of the flatness of the expansion curve instead of or in addition to the parameter F, in which case the expansion curve is considered not in the temperature range (0;50) but in another temperature interval (Ti), preferably in the temperature ranges (0;80), (0;100), (20;40), (20;70) and / or (−10;30). This allows the expansion behavior to be better classified with respect to the application area at a later time.

[0133] Alternative parameter f T.i. has units (ppm / K) and is as follows: f T.i. =TCL (T.i.) / Temperature range (Ti) width (4) where Ti represents the respective considered temperature interval.

[0134] TCL (T.i.) The value is the difference between the highest and lowest dl / l0 values ​​in the respective considered temperature range (Ti), where the expansion curve is (T.i.) The determinations are also normalized by definition so that the length change at 0°C is 0 ppm. For example: TCL (20;40℃) =|dl / l0max.|+|dl / l0min.| (5) where "dl" represents the change in length at each temperature, and "l0" represents the length of the specimen at 0°C. The calculation is based on the absolute value of the dl / l0 value.

[0135] Alternative parameter f T.i. is expressed as TCL according to equation (4). (T.i.)It is calculated by taking the quotient of the value [in ppm] (see above) and the width, in [K], of the temperature interval (Ti) for which the expansion difference is taken into account. The width of the considered temperature interval from 20°C to 40°C is 20 K. On the other hand, if the progression of the expansion curve in the interval Ti = (20; 70) or (-10; 30) is taken into account, the denominator of equation (4) is 50 K or 40 K, respectively.

[0136] In one advantageous embodiment, the glass ceramic has an alternative parameter f<0.024 ppm / K. (20;40) and / or an alternative parameter f of <0.039 ppm (20;70) and / or an alternative parameter f of <0.015 ppm / K (-10;30) It has.

[0137] Glass ceramics with very flat expansion curves are very advantageous, since precision components can now be optimized not only for later application temperatures, but also for higher and / or lower temperature loads that may be expected, for example. T.i. is suitable for specifying suitable materials according to the specifications required for a particular component application and providing corresponding precision components. Specific precision components and their applications are described below and incorporated herein.

[0138] According to an advantageous embodiment of the glass ceramic or a component made therefrom, the alternative parameter f (20;40) It may be advantageous if the expansion coefficient is <0.024 ppm / K, preferably <0.020 ppm / K, preferably <0.015 ppm / K. Hysteresis-free, zero-expansion components with such expansion behavior in the temperature range (20;40) are particularly well suited at room temperature as precision components for microlithography and EUV microlithography. An example of such an advantageous glass-ceramic is shown in FIG. 9.

[0139] According to an advantageous embodiment of the glass ceramic or a component made therefrom, the alternative parameter f (20;70)It may be advantageous if the thermal expansion coefficient is <0.039 ppm / K, preferably <0.035 ppm / K, preferably <0.030 ppm / K, preferably <0.025 ppm / K, preferably <0.020 ppm / K. Hysteresis-free, zero-expansion components with such expansion behavior in the temperature range (20;70) are also particularly well suited as precision components for microlithography and EUV microlithography. It is particularly advantageous if the components also exhibit low thermal expansion when subjected to higher temperature loads, which may occur, for example, locally or over a large area, during the manufacture of the precision component as well as during operation. Further details of the temperature loads occurring in EUVL precision components have already been given above with regard to the parameter F, and reference is made thereto to avoid repetition. An example of such an advantageous glass-ceramic is shown in FIG. 7.

[0140] According to an advantageous embodiment of the glass ceramic or a component made therefrom, the alternative parameter f (-10;30) It may be advantageous if the expansion coefficient is <0.015 ppm / K, preferably <0.013 ppm / K, preferably <0.011 ppm / K. Hysteresis-free, zero-expansion components with such expansion behavior in the temperature range (-10;30) are particularly well suited as precision components, in particular as mirror substrates for applications in which temperatures below room temperature may also occur, for example in astronomy or Earth observation from outer space. Corresponding components are described below.

[0141] A particularly advantageous embodiment of the glass ceramic or a component made therefrom is characterized by the alternative parameter f (T.i.) The expansion curves satisfy at least two of the following conditions.

[0142] A particularly advantageous embodiment of the glass ceramic or a component made therefrom is characterized by a parameter F and an alternative parameter f (T.i.) The expansion curve satisfies at least one of the following:

[0143] CTE Plateau Figures 1 to 4 show advantageous embodiments of LAS glass ceramics and precision parts having a CTE "plateau". Glass ceramics having a plateau, i.e., zero expansion optimized over a wide temperature range, provide the same advantages already described above with respect to the flat transition of the expansion curve and parameter F.

[0144] When the differential CTE shows a plateau close to 0 ppm / K, i.e., in a temperature interval T having a width of at least 40 K or at least 50 K or at least 60 K or at least 70 K P it is advantageous if the differential CTE is less than 0 ± 0.015 ppm / K in T. The temperature interval of the CTE plateau is denoted as T P Advantageously, in the temperature interval T having a width of at least 40 K or at least 50 K P the differential CTE may be less than 0 ± 0.010 ppm / K or less than 0 ± 0.005 ppm / K.

[0145] Thus, the CTE "plateau" is understood to be the range over which the differential CTE extends over a region of the CTE-T curve that does not exceed a value of 0 ± 0.015 ppm / K or 0 ± 0.010 ppm / K or 0 ± 0.005 ppm / K, i.e., a CTE near 0 ppb / K.

[0146] Advantageously, in the temperature interval T having a width of at least 40 K P the differential CTE may be less than 0 ± 0.015 ppm / K, i.e., 0 ± 15 ppb / K. In a preferred embodiment, a CTE plateau of 0 ± 0.01 ppm / K, i.e., 0 ± 10 ppb / K, may be formed over a temperature interval of at least 50 K.

[0147] The temperature interval T P may advantageously be in the range of -10 to +100 °C or 0 to 80 °C or 15 to 80 °C.

[0148] The position of the CTE plateau of the glass ceramic is preferably the application temperature T of the precision part AIt is adapted to T P =T A ±x, where x is selected from the group consisting of 20, 25, 30 or 40. Preferred application temperatures T A is in the range of -60°C to +100°C, more preferably -40°C to +80°C. Particular variants of the invention are applied at temperatures T of 0°C, 5°C, 10°C, 22°C, 40°C, 60°C, 80°C and 100°C. A The CTE plateau, i.e., the temperature range T p The curve range with small deviations in the differential CTE can also be in the temperature ranges of [-10;100];[0;80], [0;30°C], [10;40°C], [20;50°C], [30;60°C], [40;70°C] and / or [50;80°C].

[0149] Figure 1, using Example 4 from Table 1, shows that this glass-ceramic has a CTE of 0±0.010 ppm / K over the indicated temperature range of 15°C to 90°C, i.e., a plateau of 10 ppb at 75 K. The glass-ceramic also has a CTE of 0±0.005 ppm / K over the temperature range of 17°C to 85°C, i.e., a plateau of 5 ppb at about 70 K.

[0150] FIG. 2 shows for Example 2 from Table 1 that this glass-ceramic has a CTE of 0±0.010 ppm / K between 12° C. and 90° C., i.e., a plateau of 10 ppb width at 78 K.

[0151] FIG. 3 shows for Example 2 a glass-ceramic with an optimized CTE plateau (CTE of 0±0.005 ppm / K, i.e., with a 5 ppb plateau) in the temperature range of −10 to 23° C.

[0152] Figure 4 shows that for Example 6 from Table 1, the glass-ceramic has a CTE of 0 ± 0.005 ppm / K, i.e., a 5 ppb plateau, over the temperature range of 15-30°C relevant to EUV lithography. This glass-ceramic meets the average CTE (19;25) requirement set forth in the SEMI P37-1109 standard for EUVL substrates and blanks. The zero crossing of this CTE-T curve is at 22°C.

[0153] Another indicator for favoring thermal expansion is the slope of the CTE-T curve, which can be obtained by differentiating the CTE-T curve. Thus, according to an advantageous embodiment of the invention, the CTE-T curve of the glass ceramic or precision component has at least one curve section with a low slope, in particular a slope of at most 0±1.5 ppb / K. 2 , advantageously at most 0±1.0 ppb / K 2 , advantageously at most 0±0.8 ppb / K 2 , preferably at most 0±0.7 ppb / K 2 , preferably at most 0±0.6 ppb / K 2 and, according to a special variant, even up to only 0±0.5 ppb / K. 2 is.

[0154] The temperature range with a small slope is preferably the application temperature T A It is adapted to T P =T A ±x, where x is selected from the group consisting of 10, 15, 20, 25, 30 or 40. Preferred application temperatures T A is in the range of -60°C to +100°C, more preferably -40°C to +80°C. Particular variants of the invention are those with application temperatures T of 0°C, 5°C, 10°C, 22°C, 40°C, 60°C, 80°C and 100°C. A The temperature interval with a small slope can be in the temperature ranges [-10; 100], [0; 80], [0; 30°C], [10; 40°C], [20; 50°C], [30; 60°C], [40; 70°C] and / or [50; 80°C].

[0155] 10-12 show the slope of the CTE-T curves for the advantageous glass-ceramics according to Examples 4, 2, and 5 in the temperature range of -10°C or 5°C to 45°C. The slope of the CTE is 0±1.0 ppb / K over the entire temperature range. 2 is less than.

[0156] FIG. 13 shows the slope of the CTE-T curve for a glass-ceramic having the same composition as Example 9 over the temperature range of −5°C to 45°C, which has been ceramized to have an average CTE[0;50°C] of −0.009 ppm / K.

[0157] Glass ceramics and precision components with such expansion behavior are particularly well suited for EUV lithography applications (e.g., as mirrors or substrates for mirrors or masks or mask blanks), since in this field increasingly high demands are being made on materials and precision components used in optical components with extremely low thermal expansion, zero crossings of the CTE-T curve near the application temperature, and in particular low slopes of the CTE-T curve. Advantageous embodiments of glass ceramics or precision components within the scope of the present invention exhibit very flat CTE curves, which in addition to the zero crossings also exhibit very low CTE slopes and, in some cases, also very flat plateaus.

[0158] The low slope feature can be present with or without the formation of a favorable CTE plateau.

[0159] Other characteristics The advantageous glass ceramics and precision components made therefrom further exhibit good internal quality. Preferably, they are 100 cm 3 A maximum of 5 inclusions per 100cm² is preferred. 3 Maximum of 3 inclusions per 100cm, most preferably 3 According to the invention, inclusions are understood to be both bubbles and crystallites with a diameter of more than 0.3 mm.

[0160] According to a variant of the invention, the diameter or side length is at most 800 mm and the thickness is at most 100 mm, and the inclusions with a diameter greater than 0.03 mm are each 100 cm 3 At most five, preferably at most three, more preferably at most one precision part per unit are provided.

[0161] In addition to the number of inclusions, the maximum diameter of the detected inclusions also serves as an indicator of the grade of internal quality. The maximum diameter of individual inclusions in the total volume of glass-ceramics with a diameter of less than 500 mm is preferably at most 0.6 mm, and in application-critical volumes, e.g., near the surface, it is preferably at most 0.4 mm. The maximum diameter of individual inclusions in precision components with a diameter of 500 to less than 2 mm is preferably at most 3 mm, and in application-critical volumes, e.g., near the surface, it is preferably at most 1 mm.

[0162] The invention further relates to the use of the glass ceramic according to the invention in precision components. The glass ceramic can, for example, form the substrate of a precision component or can represent the precision component itself.

[0163] All of the properties and ranges of the glass ceramic mentioned above also apply to precision components which contain or consist of this glass ceramic.

[0164] Furthermore, the invention relates to the use of the glass ceramics according to the invention in precision parts, in particular in metrology, spectroscopy, measuring technology, lithography, astronomy or Earth observation from outer space, for example as mirrors or mirror substrates for segmented or integrated astronomical telescopes, or even as lightweight or ultra-lightweight mirror substrates, for example for space-based telescopes, or as high-precision structural elements, for example for distance measurements in space, or as optical systems for Earth observation, as standards for precision measuring technology, precision scales, reference plates in interferometers, mechanical precision parts, for example for ring laser gyroscopes, spiral springs in the watch industry, as mirrors and prisms, for example in LCD lithography, and as mask holders, wafer stages, reference plates, reference frames and grid plates in microlithography and EUV (extreme UV) microlithography, and also as mirrors or mirror substrates and / or photomask substrates or photomask blanks or reticle mask blanks in EUV microlithography.

[0165] The glass ceramic according to the invention can be used to manufacture precision components of various sizes.

[0166] One embodiment relates to precision parts with small dimensions, in particular with a side length (width and / or depth) of at least 100 mm and / or at most 1500 mm in the case of angled (right-angled) shapes or a diameter of at least 1500 mm in the case of circular surfaces, and / or a thickness of less than 50 mm, preferably less than 10 mm and / or at least 1 mm, more preferably at least 2 mm. Such precision parts can be used, for example, in microlithography and EUV lithography.

[0167] Another embodiment relates to precision components with very small dimensions, in particular with a side length (width and / or depth) or diameter and / or thickness of a few mm (for example at most 20 mm or at most 10 mm or at most 5 mm or at most 2 mm or at most 1 mm) to a few tenths of a mm (for example at most 0.7 mm or at most 0.5 mm). These precision elements can be, for example, spacers in interferometers or parts of ultra-stable clocks in quantum technology.

[0168] However, very large precision parts can also be produced. Therefore, one embodiment of the present invention relates to large-volume parts. This is to be understood in the sense of the present application as parts weighing at least 300 kg, preferably at least 400 kg, preferably at least 500 kg, preferably at least 1 t, more preferably at least 2 t, and according to one variant of the invention, at least 5 t, or parts with a side length (width and / or depth) of at least 0.5 m, more preferably at least 1 m, and a thickness (height) of at least 50 mm, preferably at least 100 mm, if they are angled (right-angled), or parts with a diameter of at least 0.5 m, more preferably at least 1 m, more preferably at least 1.5 m, and / or a thickness (height) of at least 50 mm, preferably at least 100 mm, if they are circular. In particular embodiments of the invention, parts may be even larger, for example with a diameter of at least 3 m or at least 4 m or more. According to one variant, the invention also relates to rectangular parts, preferably with at least one surface having a thickness of at least 1 m. 2 , preferably at least 1.2 m 2 , more preferably at least 1.4 m 2 Typically, large volume parts are manufactured whose base area is significantly greater than their height. However, it may also be large volume parts whose shape approximates a cube or sphere.

[0169] The precision component may be, for example, an optical component, i.e., a so-called normal incidence mirror, i.e., a mirror operating near normal incidence of radiation, or a so-called grazing incidence mirror, i.e., a mirror operating at grazing incidence of radiation. Such mirrors, in addition to a substrate, comprise a coating that reflects the incident radiation. In particular, in the case of an X-ray mirror, the reflective coating is, for example, a multilayer system or multilayer having several layers with high reflectivity in the X-ray range at non-grazing incidence. Preferably, such a multilayer system for a normal incidence mirror comprises 40 to 200 pairs of alternating layers of one of the material pairs, e.g., Mo / Si, Mo / Bi, Ru / Si, and / or MoRu / Be.

[0170] In particular, the optical elements according to the invention can be X-ray optical elements, i.e. optical elements used in combination with X-rays, especially soft X-rays or EUV radiation, in particular reticle masks or photomasks operating in reflection, especially for EUV microlithography. Advantageously, they can be mask blanks. Even more advantageously, the precision components can be used as mirrors for EUV lithography or as substrates for mirrors for EUV lithography.

[0171] Furthermore, the precision component according to the present invention can be a component, in particular a mirror for astronomy. Such astronomy components can be used both on the ground and in space. Another advantageous application area is high-precision structural components for distance measurement in space, for example.

[0172] The precision part according to the present invention may have a lightweight structure. The part according to the present invention may further include a lightweight structure. This means that cavities are provided in some areas of the part to reduce the weight. Preferably, the weight of the part is reduced by at least 80%, more preferably at least 90%, by the lightweight processing compared to the unprocessed part.

[0173] The present invention further relates to a precision component comprising an LAS glass ceramic according to the invention, details of which have already been mentioned above in connection with the glass ceramic and its use in precision components, the disclosure of which is fully included in the description of the precision component.

[0174] It is understood that the features mentioned above and those to be described below can be used in each combination not only shown but also in other combinations without departing from the scope of the invention.

[0175] Example Tables 1 to 4 show the compositions of examples of glass ceramics according to the present invention and comparative examples, as well as their properties.

[0176] The compositions were melted using conventional manufacturing methods from commercially available raw materials, such as oxides, carbonates, and nitrates. The resulting green glasses were first ceramized at the maximum temperatures specified for the periods indicated.

[0177] The glass-ceramic production of precision components, in particular large precision components, is described, for example, in WO 2015 / 124710.

[0178] In the tables below, if a column for composition data is blank, this means that this component(s) was not intentionally added or included. The tables show the absolute value of the hysteresis.

[0179] [Table 1]

[0180] [Table 2]

[0181] [Table 3]

[0182] Table 4

Claims

1. LAS glass ceramic, having a maximum of 0±0.02×10 in the range of 0 to 50°C －６ / K and a thermal hysteresis of <0.1 ppm over the temperature range of at least 10°C to 35°C, and containing the following components (in mole % on an oxide basis): Yes ２ 60~70 Li ２ O7~9.4 R ２ O(R=Na、K、Cs、Rb) 0.7~2.0 MgO+ZnO 0~0.4 P ２ O ５ and at least one component selected from the group consisting of RO, wherein RO may be CaO and / or BaO and / or SrO; and A nucleating agent having a content of 1.5 to 6 mol % and containing TiO ２ , ZrO ２ , Ta ２ O ５ , Nb ２ O ５ , SnO ２ , MoO ３ , W.O. ３ a nucleating agent, which is at least one component selected from the group consisting of LAS glass ceramics, including

2. The following components (in mole % on an oxide basis): Yes ２ 60~70 Li ２ O7~9.4 R ２ O(R=Na、K、Cs、Rb) 0.7~2.0 MgO+ZnO 0~0.4 BaO 0 to <0.5 P ２ O ５ and at least one component selected from the group consisting of RO, wherein RO may be CaO and / or SrO; and A nucleating agent having a content of 1.5 to 6 mol % and containing TiO ２ , ZrO ２ , Ta ２ O ５ , Nb ２ O ５ , SnO ２ , MoO ３ , W.O. ３ a nucleating agent, which is at least one component selected from the group consisting of The LAS glass-ceramic of claim 1 , comprising:

3. The following components (in mole % on an oxide basis): Yes ２ 60~70 Li ２ O7~9.4 K ２ O 0.7~2.0 Na ２ O0~0.4 MgO+ZnO 0~0.4 P ２ O ５ and at least one component selected from the group consisting of RO, wherein RO may be CaO and / or BaO and / or SrO; and A nucleating agent having a content of 1.5 to 6 mol % and containing TiO ２ , ZrO ２ , Ta ２ O ５ , Nb ２ O ５ , SnO ２ , MoO ３ , W.O. ３ a nucleating agent, which is at least one component selected from the group consisting of The LAS glass-ceramic of claim 1 , comprising:

4. The following components (in mole % on an oxide basis): Yes ２ 60~70 Li ２ O7~9.4 K ２ O 0.7~2.0 Na ２ O0~0.4 MgO+ZnO 0~0.4 BaO 0 to <0.5 P ２ O ５ and at least one component selected from the group consisting of RO, wherein RO may be CaO and / or SrO; and A nucleating agent having a content of 1.5 to 6 mol % and containing TiO ２ , ZrO ２ , Ta ２ O ５ , Nb ２ O ５ , SnO ２ , MoO ３ , W.O. ３ a nucleating agent, which is at least one component selected from the group consisting of The LAS glass-ceramic of claim 1 , comprising:

5. Al having a content of 10 to 22 mol%, preferably 11 to 21 mol% ２ O ３ and / or P having a content of 0.1 to 6 mol %, preferably 0.3 to 5 mol % ２ O ５ 2. The LAS glass-ceramic of claim 1, comprising:

6. - Al ２ O ３ If the molar content is <17.0 mol % and preferably ≥ 15.8 mol %, - SiO ２ is 63.5 mol % to 65.6 mol %, - 30.7≦(SiO ２ Molar content - (2 x Al ２ O ３ molar content) applies; or - Al ２ O ３ If the molar content is ≧17.0 mol % and preferably ≦19.0, - SiO ２ is 62.0 mol % to 66.0 mol %, - 142.5≦(SiO ２ Molar content + (4.6 × Al ２ O ３ The following applies: molar content))≦149.0; The LAS glass ceramic of claim 5.

7. 2. The LAS glass ceramic according to claim 1, wherein the total content of ZnO+MgO is ≦0.2 mol %, or ≦0.1 mol %, or ≦0.05 mol %, and / or the content of MgO is ≦0.4 mol %, ≦0.2 mol %, or ≦0.1 mol %, or ≦0.05 mol %, and / or the content of ZnO is ≦0.4 mol %, ≦0.2 mol %, or ≦0.1 mol %, or ≦0.05 mol %, and / or the LAS glass ceramic is free of ZnO and / or MgO.

8. 2. The LAS glass ceramic according to claim 1, wherein the total content of nucleating agents is ≥ 1.5 mol %, preferably ≥ 2.5 mol %, advantageously ≥ 3 mol % and / or ≤ 6 mol %, advantageously ≤ 5 mol %, preferably ≤ 4.5 mol %, preferably ≤ 4 mol %.

9. Up to 0.05 mol% As as a fining agent ２ O ３ 2. The LAS glass-ceramic of claim 1, comprising:

10. The LAS glass ceramic contains, as a fining agent, As ２ O ３ or up to 0.05 mol % As ２ O ３ and / or at least one alternative redox fining agent and / or at least one evaporation fining agent and / or at least one decomposition fining agent, and / or the alternative redox fining agent is Sb ２ O ３ , SnO ２ , MnO ２ , CeO ２ , Fe ２ O ３ and / or the evaporative fining agent contains a halogen having a fining effect, and / or the decomposition fining agent contains a sulfate component.

11. 2. The LAS glass ceramic according to claim 1, wherein the total length change TCL is TCL(0;50)<0.2 or TCL(0;50)<0.

1.

12. 2. The LAS glass ceramic according to claim 1, wherein the differential CTE exhibits a plateau around 0 ppm / K, i.e., the differential CTE is less than 0±0.010 ppm / K or less than 0±0.005 ppm / K in a temperature interval TP having a width of at least 40 K or at least 50 K.

13. 2. The LAS glass ceramic according to claim 1, wherein the temperature section TP is in the range from -10 to +100°C, or from 0 to 80°C, or from 15 to 80°C.

14. The CTE-T curve in a temperature range TP having a width of at least 30 K is at most ±1 ppb / K. ２ 2. The LAS glass ceramic of claim 1, wherein the LAS glass ceramic has a gradient of:

15. 2. The LAS glass ceramic according to claim 1, wherein the processing temperature Va is at most 1330°C, preferably at most 1320°C.

16. The CTE-T curve in a temperature range having a width of at least 30 K is ≦0±2.5 ppb / K. ２ , preferably ≦0±2 ppb / K ２ , preferably ≦0±1.5 ppb / K ２ , particularly preferably ≦0±1 ppb / K ２ 2. The LAS glass ceramic of claim 1, wherein the LAS glass ceramic has a gradient of:

17. 2. The LAS glass ceramic according to claim 1, which exhibits a thermal hysteresis of <0.1 ppm at least in the temperature range from 5°C to 45°C, advantageously at least in the temperature range from >0°C to 45°C, preferably at least in the temperature range from -5°C to 50°C.

18. 10. Precision parts comprising the LAS glass ceramic according to claim 1 for use in metrology, spectroscopy, measuring technology, lithography, astronomy or Earth observation from outer space, for example as mirrors or mirror substrates for segmented or integrated astronomical telescopes, or also, for example, as lightweight or ultra-lightweight mirror substrates for space-based telescopes, or as high-precision structural elements, for example for distance measurements in space, or as optical systems for Earth observation, for example as standards for precision measuring technology, precision scales, reference plates in interferometers, mechanical precision parts, for example for ring laser gyroscopes, as spiral springs in the watch industry, as mirrors and prisms, for example in LCD lithography, as mask holders, wafer stages, reference plates, reference frames and grid plates in microlithography and EUV microlithography, and as mirrors and / or photomask substrates or reticle mask blanks in EUV microlithography.

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