JP6835659B2 - Crystallizable Lithium Aluminum Silicate Glass, and Transparent Glass Ceramics Made From It, and Methods for Making Glass and Glass Ceramics, and Use of Glass Ceramics. - Google Patents

Description

The present invention relates to a crystallizable lithium aluminum silicate glass that can be converted into a transparent LAS glass ceramic according to the superordinate concept of claim 1.

The present invention also relates to glass ceramics made from this crystallizable lithium aluminum silicate glass, methods of making the glass ceramics, and the use of such LAS glass ceramics.

It is generally known that a glass composed of Li ₂ O-Al ₂ O _3- SiO ₂ system can be converted into a glass ceramic containing a high quartz mixed crystal or a catetite mixed crystal as a main crystal phase. In the literature, the first type of glass-ceramic is synonymous with "β-quartz" or "β-eucryptite", and the second type is referred to as "β-spojumen". Seen as the name for.

An important characteristic of this LAS glass ceramic, transparency, good chemical resistance to acids and alkalis, high mechanical strength, and room temperature of ^{_{α 20/700 <1.5 · 10 -6 /}} K to the application temperature It has a low coefficient of thermal expansion in the temperature range. In principle, this thermal expansion behavior is adjusted so that the material provides ^{very slight expansion, usually 0 ± 0.3.10-6 / K, within its applicable temperature range.} Thermal expansion in the room temperature region, for example, when applied as a substrate material such as color filters, display displays, sensors, semiconductor substrates-precision tables (also called wafer stages), or as mirror supports for telescopes. Is minimized.

For application as a fireproof glass window, as a transparent fireplace viewing window, as a furnace viewing window outside or inside the furnace, and as a cooking table with a colored undercoat, in the temperature range from room temperature to about 700 ° C. The thermal zero expansion is adjusted to as low a value as possible ^{, <1.5.10-6} / K, preferably 0 ± ^{0.3.10-6 / K.} Based on the low thermal expansion at this application temperature combined with the high mechanical strength, this glass ceramic exhibits excellent temperature difference stability and temperature change durability. Requirements for use at high temperatures include that the glass ceramic maintains the required properties (eg, thermal expansion, transmission, stress formation) over its lifetime. With respect to temperature durability, even the slightest compaction of glass-ceramics is significant at high temperatures. Glass-ceramic products are often unevenly warmed during their use, resulting in the formation of stress within the product due to different significant shrinkage over time.

Transparency associated with slight scattering is an important feature that distinguishes clear glass ceramics from colored clear glass ceramics. _{In the latter case, V 2} O ₅ is generally added for countertop coloring, especially for coloring in bulk, in order to reduce light transmission and achieve a black appearance. In the case of colored transparent glass-ceramics, the light transmittance is usually less than 30%, usually less than 10% (4 mm thickness), compared to more than 80% for the transparent type light transmittance. in the case of).

When applied as a countertop, the clear glass-ceramic plate has an often opaque colored coating on the underside to prevent the technical assembly from being seen and to provide a colorful impression. Be prepared. The voids in the undercoat allow for the installation of colored and white display displays, often light emitting diodes. The high transparency associated with slight scattering is important even in this application because it does not alter the color tone of the undercoat and the display and the display is clearly and clearly visible.

High transparency means high light transmittance and slight color tone, thereby meaning slight absorption, because the context-sensitive absorption band in the visible spectrum reduces the light transmittance and This is to enhance the color tone.

The light transmittance is represented by the Y value (luminance) according to the CIE standard color system. The transition of the international CIE standard in Germany is specified in DIN 5033. The spectrophotometer measurements required for this are performed within the scope of the present invention in the spectral region of 380-780 nm for a polished sample with a thickness of 4 mm. From the spectral values measured in the range representing the visible spectrum, the light transmittance is calculated by selecting standard light and observation angle.

In the case of glass-ceramics, ^{it is widespread to consider the parameter c *} (saturation) from the CIELAB color system along with ^{the coordinates L *} , a ^* , b ^* as a measure of color tone according to the following equation:

This color model is standardized by DIN EN ISO 11664-4 "Colorimetry --Part 4: CIE 1976 L * a * b * Color space". As is known, the coordinates of the CIELAB color system can be calculated from the chromaticity coordinates and the light transmittance Y of the CIE color system. The determination of the c ^* value of the sample is made from the spectrophotometer measurements of the transmittance at the parameters selected for standard light and observation angle.

The scattering of glass-ceramics is determined by the measurement of cloudiness (English: haze). Haze is the percentage of light that is transmitted by ASTM D1003-13 with an average deviation of more than 2.5 ° from the incident light flux.

Large-scale industrial production of transparent glass-ceramics is carried out in multiple stages. First, crystallizable starting glass is melted and clarified from a mixture consisting of cullet and powdered mixed raw materials. The glass melt is allowed to reach temperatures, in this case, from 1550 ° C to a maximum of 1750 ° C, usually up to 1700 ° C. In some cases, high temperature clarification above 1700 ° C., usually at a temperature of about 1900 ° C., can also be used. For clear glass ceramics, arsenic oxide and antimony oxide are industrially and economically proven fining agents for good bubble quality at normal fining temperatures below 1700 ° C. Arsenic oxide is particularly preferred for the transparency of glass-ceramics (high light transmittance and slight color tone). This fining agent is a drawback in terms of safety and environmental protection, even when it is tightly integrated within the glass skeleton. Special precautions must be taken, for example, in raw material harvesting, raw material preparation, and for evaporation from the melt in the case of glass making. Therefore, there are numerous development efforts to replace this material, but these development efforts face industrial and economic shortcomings.

_{As an alternative, the eco-friendly fining agent SnO 2} alone or in combination with one or more fining additives such as halides (F, Cl, Br), CeO ₂ and sulfur compounds is becoming increasingly popular. However, _{the use of SnO 2} is associated with drawbacks. SnO ₂ itself is not very industrially effective as a fining agent and requires a relatively high temperature to release oxygen for fining activity. However, _{a relatively high concentration of SnO 2} at about 0.6-1% by weight of _{the As 2} O ₃ scale used is disadvantageous due to devitrification of Sn-containing crystals during thermoforming. For transparent glass-ceramics, the second essential drawback of replacing arsenic oxide with tin oxide as a fining agent is that SnO ₂ causes additional absorption and enhances color tone. At relatively high clarification temperatures, this absorption is enhanced, as this absorption increases with increasing ^{Sn 2+ proportions.}

Japanese Patent Application Laid-Open No. 11-228180 (JP 11-228180 A2) and Japanese Patent Application Laid-Open No. 11-228181 (JP 11-228181 A2) describe _{the fining agents of SnO 2} 0.1 to 2% by mass and Cl. The combination of arsenic oxide-free LAS glass environmentally friendly clarifications is described. The _{yellowish brown hue associated with the use of SnO 2} is an extreme drawback for clear glass ceramics. These documents do not provide the suggestion that _{SnO 2} content should be limited to ensure slight absorption and sufficient devitrification resistance.

_{The union clarification of SnO 2} in combination with a fluorine compound or a boron compound can be found in the European Patent Application Publication No. 1899276 (EP 1 899 276 A1) or European Patent Application Publication No. 1901999 (EP 1 901 999 A1). It is disclosed in. However, these halides are problematic from an environmental point of view due to their evaporation and are disadvantageous with respect to corrosion of the built-in members during melting and molding.

After melting and clarification, the glass is thermoformed, usually by roll, casting, stamping, or float method. For most applications of clear glass-ceramic, this glass-ceramic is required in the form of a flat surface, eg, a plate. The roll method and, more recently, the float method are also used for the production of this plate. On the one hand, a low melting temperature and a low processing temperature _VA during thermoforming are desirable for the economical production of this LAS glass. On the other hand, the glass must not exhibit devitrification during molding, i.e., it must not form annoying crystals in the glass-ceramic product that reduce its strength or interfere visually. The critical coldest region during molding by the roll method is the contact area between the glass melt and the extraction nozzle made of a noble metal (usually a Pt / Rh alloy) prior to the molding and cooling of the glass by the roll.

Crystallizable LAS glass is converted to glass-ceramic by controlled crystallization (ceramicization) in a subsequent temperature process. This ceramicization is carried out in a two-step temperature process, where first nucleation at a temperature of 680-800 ° C. produces nuclei, usually composed of ZrO ₂ / TiO ₂ mixed crystals. SnO _{2 is} also involved in this nucleation. High quartz mixed crystals grow on this nucleus at elevated temperatures. At a maximum production temperature of about 900 ° C., the structure of the glass-ceramic is homogenized and its optical, physical and chemical properties are adjusted. Short ceramicization times are preferred for economical production.

Further conversion to a catetite mixed crystal is carried out during temperature rise in the temperature range from about 950 ° C to 1250 ° C. This conversion increases the coefficient of thermal expansion of the glass-ceramic, and further crystal growth, and the accompanying light scattering, transforms the transparent appearance into a translucent to opaque appearance.

_{An essential obstacle to the use of SnO 2} as an environmentally friendly fining agent is the additional absorption by the resulting Sn / Ti complex. This Sn / Ti colored composite is significantly more colored than the known Fe / Ti colored composite, and this drawback is that it has been difficult to replace _{arsenic oxide with SnO 2 as a fining agent in the case of transparent glass ceramics.} I was doing it. This Sn / Ti colored composite has been found to be a drawback, especially due to the enhanced color tone c ^*. This Fe / Ti colored complex causes a reddish-brown color tone, and the Sn / Ti colored complex causes a yellow-brown color tone. The absorption mechanism of both colored complexes is speculated to be based on electron transfer (charge transfer) between two adjacent polyvalent cations. The formation of the listed charge transfer colored complexes occurs decisively during crystallization. It is preferable to shorten the nucleation time and the crystallization time in order to reduce the concentration of the colored complex. This contradicts that shortening the nucleation time causes enhanced light scattering and shortening the crystallization time causes non-flatness of the product.

Other coloring elements such as Cr, Mn, Ni, V and especially Fe are contained as impurities in the industrial mixed raw material for the melt. This Fe is ionicly colored as ^{Fe 2+} or Fe ³⁺ , in addition to the Fe / Ti colored composite. Due to the high cost of iron-poor raw materials, _{it is uneconomical to reduce the Fe 2} O ₃ content to a value of less than 100 ppm.

Similarly, avoid TiO ₂ effective nucleating agents which cause colored complex (WO 2008/065167 (WO 2008/065167 A1)) or restrict (WO 2008/065166 (WO 2008/065166 A1)) attempts have not caused an industrial transition so far. The required increased content of another nucleating agent ZrO ₂ and / or SnO ₂ is a relatively high melting and molding temperature for melting and molding, as well as insufficient devitrification resistance during molding. It causes such drawbacks.

WO 2013/124373 (WO 2013/124373 A1) is a transparent glass-ceramic that is free of arsenic and antimony except for unavoidable raw material impurities and contains a high quartz mixed crystal as the main crystal phase. Physical decolorization with the addition of 0.15% by weight Nd ₂ O _{3 is described.} The principle of this bleaching is based on the existing absorption bands being neutralized by the complementary absorption bands of the bleaching agent. This, of course, causes stronger absorption of light, thereby reducing light transmission. In order to achieve favorable production conditions, i.e. low melting temperature and low molding temperature, the examples glass of this document contains 0.44 to 0.93% by mass of a viscosity reducing component MgO. MgO + ZnO> CaO + SrO + BaO in the overall relationship of the divalent components described to regulate the crystal composition and the composition of the residual glass phase means an increased MgO content.

International Publication No. 2013/171288 (WO 2013/171288 A1) provides clear, essentially light-colored, non-scattering glass-ceramic products, glass-ceramics and precursor glasses, including high-quartz mixed crystals. It is disclosed. The composition of LAS glass-ceramics is free of arsenic oxide, antimony oxide and rare earth oxides such as _{Nd 2} O _{3 except for the unavoidable trace content.} The disclosed compositions are SiO ₂ 62 to 72% by mass, Al ₂ O ₃ 20 to 23% by mass, Li ₂ O 2.8 to 5% by mass, SnO ₂ 0.1 to 0.6% by mass, TiO ₂ 1 .9～4 wt%, including ZrO ₂ 1.6 to 3 wt%, MgO less than 0.4 wt%, a 2.5 to 6 wt% Fe ₂ O ₃ 250 ppm and less than ZnO + BaO + SrO. The average crystallit size is less than 35 nm. The drawback of the composition claimed here is, in addition to the high melting temperature, a particularly high processing temperature _VA , which is a narrow processing tolerance based on a relatively high temperature for molding using the roll method. Means low range and low service life of the device.

US Patent Application Publication No. 2013/0130887 (US 2013/0130887 A1) describes SiO ₂ 55 to 75% by mass, Al ₂ O ₃ 20.5 to 27% by mass, Li ₂ O ≥ 2% by mass, TiO ₂ Selected composition of 1.5 to 3% by mass, TiO ₂ + ZrO ₂ 3.8 to 5% by mass, SnO ₂ 0.1 to 0.5% by mass and 3.7 ≤ Li ₂ O + 0.741 MgO + 0.367 ZnO ≤ A LA glass ceramic showing a component relationship of 4.5 and SrO + 1.847CaO ≦ 0.5 is disclosed. Both of these components are said to be used to reduce the color tone of transparent glass-ceramics. This document does not provide any indication that the optimization of scattering and manufacturing properties can be achieved.

International Publication No. 2016/038319 (WO 2016/038319 A) of the literature discloses a transparent, colorless and light-scattering glass-ceramic plate containing high-zinc oxide mixed crystal type crystals, the chemical composition of which is: , As, Sb and Nd oxide- _{free, SiO 2} 55-75% by mass, Al ₂ O ₃ 12-25% by mass, Li ₂ O 2-5% by mass, Na ₂ O + K ₂ O 0 to <2 mass %, Li ₂ O + Na ₂ O + K ₂ O 0 to <7% by mass, CaO 0.3 to 5% by mass, MgO 0 to 5% by mass, SrO 0 to 5% by mass, BaO 0.5 to 10% by mass, CaO + BaO> 1 mass%, ZnO 0 to 5 mass%, TiO ₂ ≤ 1.9 mass%, ZrO ₂ ≤ 3 mass%, TiO ₂ + ZrO ₂ > 3.8 mass%, SnO ₂ ≥ 0.1 mass% were selected. The composition and the _{component relationship of SnO 2} / (SnO ₂ + ZrO ₂ + TiO ₂ ) <0.1 are shown. The minimum content of the nucleating agents TiO ₂ and ZrO ₂ is limited to avoid scattering of glass-ceramic products, and _{the maximum content of TiO 2} is limited to avoid yellowing of the products.

Therefore, all of the opposite requirements such as environmental friendliness for glass and glass ceramics and economical production of glass, glass ceramic products such as light transmittance, color tone, and scattering in a short crystallization time. There is a need to bundle them together without any quality drawbacks.

The subject underlying the present invention is
-Providing an eco-friendly composition,
-Shows favorable manufacturing characteristics for economical manufacturing,
-In less than 300 minutes of ceramicization time, it is converted to a transparent LAS glass ceramic containing a high quartz mixed crystal as the dominant crystal phase.
-Glass ceramics show a slight color tone, high light transmittance and a slight scattering,
To find crystallizable lithium aluminum silicate glass.

This problem is solved by the crystallizable lithium aluminum silicate glass according to claim 1 and the glass ceramic produced from the crystallizable lithium aluminum silicate glass.

An object of the present invention is also to find a method for producing glass and glass ceramic, and its use. These issues are solved by other independent claims.

In this case, the glass ceramic is, for example, chemical resistance, mechanical strength, transparency (low color tone, high light transmission), slight scattering, temperature durability and these properties (eg thermal expansion, transmission, stress formation). Meet application requirements such as long-term stability for changes in.
The environmentally friendly composition is interpreted as the crystallizable glass being technically free of arsenic oxide and antimony oxide as a normal fining agent, except for unavoidable raw material impurities. As impurities, both components are present in a content of less than 1000 ppm, preferably less than 500 ppm, particularly preferably less than 200 ppm. With the exception of cases, this addition is omitted when a heterogeneous cullet of transparent glass-ceramic containing arsenic oxide is added as a fining agent in the melt.

In a series of laborious tests, a narrow and limited range of compositions has been found that provides favorable manufacturing properties for LAS glass-ceramics with low color tones, high light transmittance and low scattering.

Preferred production properties for economical production include low cost mixed raw materials, low melting and molding temperatures, sufficient amount of fining agent SnO ₂ for normal clarification, devitrification resistance, and short ceramicization time. .. For short ceramicization times, high light transmission is achieved without visually disturbing light scattering (haze) or color tones.

A low melting temperature is preferred for economical production, which is ensured by the low viscosity of the glass melt at high temperatures. For this, a temperature viscosity of the glass melt is 10 ² dPas is sized to be characterized. This so-called 10 ² - temperature, the glasses of the present invention, preferably less than 1770 ° C., preferably below 1765 ° C., particularly preferably below 1760 ° C.. The low viscosity of the glass melt at high temperatures can adjust the temperature in the melt tank to a relatively low temperature, thereby extending the life of the melt tank. Energy consumption relative to the amount of glass ceramic produced is also reduced. A low glass viscosity is also preferable for bubble quality, as a low glass viscosity also promotes the rise of bubbles and thus clarification.

It is economically preferable to reduce the temperature during molding. The service life of the molding die is improved, and heat loss that is not carried out is not generated so much. Molding by a roll method or a float method in most cases is done in the viscosity of the glass melt of 10 ⁴ dPas. This temperature is also referred to as the processing temperature _VA, and is preferably a maximum of 1330 ° C, preferably a maximum of 1325 ° C for the glass according to the present invention.

This crystallizable glass provides sufficient devitrification resistance when molded from melt. During molding in contact with the molding material (eg, noble metal at the drawer nozzle in the case of a roll process), crystals that are important to the strength of the glass ceramic and are not visually noticeable are not formed in the glass. The critical temperature that causes significant devitrification, the devitrification upper limit (OEG), is preferably at least 10 ° C. below the _{processing temperature VA.} This minimum difference defines a sufficient machining tolerance for the molding process. It is particularly preferred processing tolerance of V _A -OEG is at least 20 ° C.. _VA- OEG is also a measure of devitrification resistance.

In addition, the transparent LAS glass-ceramic made from crystallizable glass meets certain properties. This light transmittance Y should be high and the color tone c ^* should be low so that the view of the object or the undercoat and the appearance of the display are not darkened or their hues. Is not modified. Clear glass-ceramics should not have light scattering that interferes with the visual sense, so the line-of-sight and display are clear and unimpaired. This should also be guaranteed when trying to achieve short ceramic times.

The content of the components responsible for the formation of the crystalline phase and the residual glass is optimized to achieve light transmission, color and scattering values in the short ceramicization time. The short crystallization time is interpreted as the glass ceramic being produced from the ceramicizable LAS glass in less than 300 minutes, preferably less than 200 minutes, particularly preferably less than 150 minutes.

In order to realize all these properties, both the crystallizable lithium aluminum silicate glass according to the present invention and the glass ceramic according to the present invention that can be produced or produced from this glass contain the following components (oxidation). (Represented by mass% based on the object):
Li ₂ O 3.4-4.1
Al ₂ O ₃ 20-22.5
SiO ₂ 64-68
Na ₂ O + K ₂ O 0.4 to 1.2
MgO 0.05 ~ <0.4
CaO 0-1
CaO + BaO 0.7-1.8
CaO + SrO + BaO 0.8 ~ 2
ZnO 0.3-2.2
TiO ₂ 1.8 to <2.5
ZrO ₂ 1.6 ~ <2.1
SnO ₂ 0.2 to 0.35
TiO ₂ + ZrO ₂ + SnO ₂ 3.8-4.8
P ₂ O ₅ 0~3
Fe ₂ O ₃ > 0.01 to 0.02
However, condition B1 (in this case, both are expressed in% by mass):
0.15 <MgO / SnO ₂ <1.7
Meet.

Preferably, condition B2 (in this case, both are expressed in% by mass):
0.4 <MgO / SnO ₂ <1.7
Meet.

These oxides Li ₂ O, Al ₂ O ₃ and SiO ₂ are in or within the stated range of the required components of the high quartz mixed crystal phase and / or the caretite mixed crystal phase.

The Li ₂ O content should be 3.4-4.1% by weight. This minimum content is required to achieve the desired low processing temperature. It has become clear that it is difficult to achieve ^{the desired low color tone c *} of glass ceramics in a short ceramicization time with a content higher than 4.1% by mass. The Li ₂ O content is preferably less than 4% by mass.

The selected content of Al ₂ O ₃ is 20 to 22.5% by mass. Higher content is disadvantageous due to the tendency of mullite to devitrify during molding. Furthermore, it was revealed that the higher content resulted in increased scattering at shorter ceramicization times. The minimum content is 20% by weight because it is advantageous due to the formation of a sufficient amount of mixed crystals and the low color tone c ^{* of the glass ceramic.} The _{minimum Al 2} O ₃ content is preferably at least 20.5% by mass.

The content of SiO ₂ should be at least 64% by weight, as is preferred due to the required properties of the glass ceramic, such as low thermal expansion and chemical durability. In addition, scattering with short ceramicization times is reduced. A minimum content of 65% by mass is particularly preferred. The SiO ₂ content should be up to 68% by weight, as this component raises the processing and melting temperatures of the glass. It _{is particularly preferable that the SiO 2} content is 67.5% by mass at the maximum.

Alkaline Na ₂ O and K ₂ O are or become components of the residual glass phase of the glass ceramic and improve meltability and devitrification during molding. Furthermore, these are preferable because they lower the processing temperature. The sum of alkaline Na ₂ O + K ₂ O should be at least 0.4% by weight. Too high a content impairs the crystallization behavior when converting a crystallizable starting glass to a glass ceramic and causes scattering with a short crystallization time. In addition, higher content causes inconvenience with respect to the color tone of the transparent glass-ceramic. The total amount of alkaline Na ₂ O + K ₂ O is preferably 1.2% by mass at the maximum, and particularly preferably 1.0% by mass at the maximum.

The component Na ₂ O was found to be favorable for low ^{color tone c *} values in a short ceramicization time. Therefore, _{the content of K 2} O is preferably less than 0.2% by mass. It is also preferable that the Na ₂ O content _{is higher than the K 2} O content (both expressed in% by mass). It is particularly preferable to satisfy the following conditions (both expressed in% by mass): Na ₂ O / K _{2 O> 2.} This condition (both expressed in% by mass) is particularly preferably> 3.

The choice of MgO content is of particular importance in order to achieve the desired properties listed for glass-ceramics. This is because MgO is both a component of mixed crystals and a component of the residual glass phase and therefore has a significant effect on many properties. These components lower the melting and processing temperatures of the glass and thus promote economical production. In glass-ceramics, these components increase thermal expansion and cause a disadvantageous increase in color tone. This is a factor in promoting the formation of Fe / Ti colored species and Sn / Ti colored species. The MgO content is 0.05 to <0.4% by mass. Preferably, the minimum content is greater than 0.1% by weight. Particularly preferably, the minimum content of MgO is 0.15% by mass. This is because, in the range of the value of MgO from 0.2% by mass to 0.35% by mass, the color tone requirement and the processing temperature requirement of the glass ceramic are particularly well related to each other.

The alkaline earths CaO, SrO and BaO are not incorporated into the mixed crystal phase and remain in the residual glass phase of the glass ceramic. These are preferable in order to reduce the melting temperature and the processing temperature. Too high a content impairs nucleation and crystallization behavior during the conversion of crystallizable glass to glass-ceramic. In addition, higher content adversely affects the time durability / temperature durability of the glass ceramic.

The component CaO has been found to be preferable for improving devitrification resistance and adjusting the refractive index of the residual glass phase. It is contained at a content of 0 to 1% by mass. This content is preferably more than 0.01% by mass, and similarly preferably up to 0.8% by mass.

In particular, it is preferable that the CaO content is at least 0.28% by mass in order to achieve both a particularly good value of devitrification resistance and a slight color tone of the glass ceramic. The upper limit of the CaO content is less than 0.5% by mass, which is particularly preferable when a particularly small amount of scattering is desired with a particularly short ceramicization time.

It is important to match the refractive indexes of the residual glass phase and the mixed crystal phase in order to reduce scattering in a short ceramicization time. This is achieved with each other by the selection of alkaline earths and especially the compositional relationships. The total of CaO + SrO + BaO of alkaline earth is 0.8 to 2% by mass.

In order to minimize color tone in addition to scattering in a short ceramic time, it is preferable that the components CaO and BaO are selected at a rather high content and the component SrO is selected at a rather low content. Therefore, this relationship applies that the sum of CaO + BaO has a content of 0.7 to 1.8% by mass. Higher content is detrimental to devitrification resistance. The ratio of alkaline earth is preferably selected so that this relationship (in this case, all expressed in% by mass): (CaO + BaO) / SrO> 3. Preferably, the SrO content is selected to be less than 0.5% by weight.

The BaO content is preferably 0 to 1.5% by mass, and the SrO content is preferably 0 to 0.5% by mass. A BaO content of at least 0.3% by mass is particularly preferred. A maximum BaO content of 1.2% by mass is particularly preferred. A SrO content of at least 0.005% by weight is particularly preferred. A maximum SrO content of 0.3% by mass is particularly preferred.

_{The selected ranges for alkaline Na 2} O, K ₂ O, and alkaline earth CaO, SrO, BaO incorporated into the residual glass phase of the glass-ceramic and their relationships are particularly short in ceramicization time. When processed, it is important to balance the desired favorable manufacturing properties of glass with a slight tint of glass ceramic, high light transmission and slight scattering.

Alkaline Na ₂ O, K ₂ O, and alkaline earths CaO, SrO, and BaO are accumulated not only in the residual glass phase, but also between crystals and on the surface of the glass ceramic. During ceramicization, a vitreous surface layer with a thickness of about 100-1000 nm is formed, which is almost crystal-free and these elements are accumulated, in which case Li ₂ O is reduced. .. This type of vitreous surface layer favorably acts on the acid resistance of the glass-ceramic surface. For this reason, the total content of alkali and alkaline earth that show these limits is important. A minimum content of both types of these components is required for sufficient thickness of the vitreous layer of at least 50 nm. In one or both types, a total content above the upper limit causes a greater thickness of the vitreous layer, which is detrimental to the strength of the glass ceramic.

The component ZnO is incorporated in the mixed crystal phase, and a part thereof remains in the residual glass phase. This component is preferably preferred for reducing the processing temperature of the glass and for reducing scattering in a short ceramicing time. The ZnO content should be at least 0.3% by weight. The ZnO content is a value of up to 2.2% by mass based on the tendency of evaporation from the glass melt and the problem of formation of an undesired crystalline phase such as Zn-spinel (garnite) during ceramicization. Limited to. A content of at least 1.1% by mass and a maximum of 2.1% by mass is preferable.

The component TiO ₂ cannot be omitted due to the transparency of the glass-ceramic as an effective nucleating agent. This causes a high nucleation rate, which in turn causes sufficient formation of nuclei, even with short crystallization times, thereby causing a small average crystallite size. Therefore, even with a short crystallization time, it is possible to obtain a glass ceramic without scattering that is visually disturbing. However, higher TiO ₂ content is important based on the formation of Fe / Ti colored and Sn / Ti colored complexes. Therefore, the TiO ₂ ratio should be between 1.8 and <2.5% by weight. _{A minimum TiO 2} content of> 1.9% by weight is preferred. _{A TiO 2} content of at least 2% by weight is particularly preferred.

_{ZrO 2} and SnO ₂ are planned as other nucleating agents. The ZrO ₂ content is limited to less than 2.1% by weight, preferably less than 2% by weight, because higher contents worsen the melting behavior of the mixture during glass production and are economical. This is because a residue may be generated in the glass depending on the amount of processing in the tank. Furthermore, during molding, the formation of Zr-containing crystals may cause devitrification. These components are advantageous for the production of glass-ceramics that exhibit ^{a low color tone c *} , as they help avoid the relatively high content of the alternative nucleating agent TiO _2. This minimum content is 1.6% by mass.

The selection of SnO ₂ content is of particular importance within the scope of the present invention. SnO ₂ is both a nucleating agent and a fining agent and therefore has a significant effect on many properties, especially important for the color of glass ceramics based on the formation of Sn / Ti colored species during crystallization. Is. _{The SnO 2} content is in the narrowly limited range of 0.2-0.35% by weight in order to take into account both the requirement for sufficient clarification and the requirement for slight color tones. Preferably, the SnO ₂ content is at most 0.33% by mass, particularly preferably at most 0.31% by mass, in order to further reduce the risk of devitrification of the Sn-containing crystals. A minimum content of greater than 0.25% by weight is particularly preferred for good clarification. A bubble quality showing the number of bubbles less than 5, preferably less than 2 per kg, especially in crystallizable starting glass or glass ceramic after clarification, is considered to be good bubble quality (0 in dimension). Measured from bubble size larger than 1 mm).

The sum of the nucleating agents TiO ₂ + ZrO ₂ + SnO ₂ should be 3.8-4.8% by weight. The minimum content is necessary for sufficiently rapid nucleation. Preferably, the minimum content is 3.9% by weight to further avoid scattering during rapid ceramicization. The upper limit of 4.8% by mass arises from the requirement for devitrification resistance.

_{P 2} O ₅ may be contained up to 3% by mass in order to improve meltability and devitrification resistance during molding. Higher content is detrimental to chemical durability and causes scattering of glass-ceramics in shorter ceramicization times. The preferred lower limit is _{0.01% by mass of P 2} O ₅ , and the preferred upper limit is 1.5% by mass. _{The upper limit of the P 2} O ₅ content of 0.8% by mass is particularly preferable. A particularly preferable lower limit is 0.02% by mass.
Addition of up to 1% by weight of B ₂ O ₃ also improves meltability and devitrification resistance, but is disadvantageous for the time durability / temperature durability of glass ceramics. Preferably, the glass-ceramic is industrially B ₂ O ₃ free, i.e. its content is less than 500 ppm.

Due to the high cost of iron-poor mixed raw materials, _{it is uneconomical to limit the Fe 2} O ₃ content of crystallizable glass to values less than 0.01% by weight, i.e. less than 100 ppm. Even when the cullet is recycled, the Fe ₂ O ₃ content is higher than 0.01% by mass because the iron is introduced through pulverization. On the other hand, the Fe ₂ O ₃ content also increases the concentration of Fe / Ti colored composites in the glass ceramic. The color tone (saturation) c ^* is increased, and the light transmittance Y (luminance) is decreased by absorption. Crystallizable glass and the glass ceramics produced from it should therefore contain up to 0.02% by weight, preferably 0.018% by weight _{, of Fe 2} O _3. For the same reason, based on the deterioration of light transmittance and color tone, glass is preferably free of other coloring compounds such as Cr, Ni, Cu, V, Mo and S compounds, except for unavoidable impurities. These contents are usually less than 2-20 ppm.

The component ratio MgO / SnO ₂ is crucial for balancing clarity, transparency and preferred manufacturing properties. A new solution has been found in the case of the present invention for matching the refractive indexes of the crystalline phase and the residual glass phase in order to avoid scattering in short ceramicization times. Color tone c ^* and light transmittance Y can be further improved without the drawbacks of economical manufacturing, or these properties do not deteriorate unacceptably at _{relatively high SnO 2 content.} ..

The glass according to the present invention _{shows a ratio of component MgO to SnO 2} (both expressed in mass%) of more than 0.15 and less than 1.7 (condition B1). This is essentially important to harmonize the desired favorable manufacturing properties of the glass with the slight tint, high light transmittance, and slight scattering of the glass ceramic even at short ceramicization times. Preferably, the ratio of component MgO to SnO ₂ is greater than 0.4 and less than 1.7 (condition B2), particularly preferably at least 0.7. Preferably, this ratio is less than 1.5, especially from 0.7 to less than 1.3. Within this preferred range in the context of the particular composition, the desired effect of minimizing color tone and light scattering during rapid ceramicization _{, which is particularly preferably associated with a low processing temperature VA, occurs.}

In the case of a preferred embodiment, both the crystallizable lithium aluminum silicate glass according to the present invention and the glass ceramic according to the present invention that can be produced from or produced from this glass contain the following components as a main component ratio ( Expressed in% by mass with reference to oxides):
Li ₂ O 3.4 to <4
Al ₂ O ₃ 20.5-22.5
SiO ₂ 65-67.5
Na ₂ O + K ₂ O 0.4 to 1.0
MgO> 0.1 to <0.4
CaO> 0.01-0.8
CaO + BaO 0.7-1.8
SrO 0-0.5
BaO 0-1.5
CaO + SrO + BaO 0.8 ~ 2
ZnO 1.1-2.1
TiO ₂ > 1.9 to <2.5
ZrO ₂ 1.6 ~ <2.0
SnO ₂ 0.2 to 0.33
TiO ₂ + ZrO ₂ + SnO ₂ 3.9-4.8
P ₂ O ₅ 0~3, preferably 0.01 to 1.5
Fe ₂ O ₃ > 0.01 to 0.018
However, condition B2:
0.4 <MgO / SnO ₂ <1.7
Meet.

In the transparent glass ceramic produced from the lithium aluminum silicate glass according to the present invention, the color tone based on the interfering Fe / Ti colored composite and / or Sn / Ti colored composite is 0 in the case of a preferred embodiment. It is reduced by the addition of _{Nd 2} O ₃ at a content of .005 mass% (50 ppm) to 0.2 mass% (2000 ppm). Nd ₂ O ₃ of less than 50ppm, the bleaching effect is slight, and Nd ₂ O ₃ exceeding 2000ppm, the light transmittance, exacerbates undesirably visible light region by absorption of Nd bands. To optimize the effects in both opposite directions, _{the content of Nd 2} O ₃ is preferably greater than 100 ppm and preferably up to 1500 ppm. A more _{preferable lower limit of Nd 2} O ₃ is 0.03% by mass, particularly 0.05% by mass.

For optimization of slight color tone of glass-ceramic, when the condition of _{Nd 2} O ₃ / Fe ₂ O _{3 > 2 is satisfied for the content of components Nd 2} O ₃ and Fe ₂ O ₃ (both expressed in mass%). Was found to be preferable. _{It is more preferable that the content Nd 2} O ₃ / Fe ₂ O ₃ is <9 so that the light transmittance is not significantly impaired.

Addition of CoO in an amount up to 30 ppm can assist in decolorization. A CoO content of 0.1 ppm to 20 ppm is preferred. The upper limit for CoO is based on the fact that it only exhibits a partial decolorizing effect and also causes a reddish tint at higher content in clear glass ceramics.

Preferably, the addition of the halogenated compound as a clarification aid is omitted. It evaporates during melting and reaches the melt tank atmosphere. In this case, corrosive compounds such as HF, HCl and HBr are formed. These are disadvantageous due to the corrosion of refractory bricks in the melt tank and in the exhaust gas line. Therefore, glass and glass-ceramic are free of F, Cl, Br, except for unavoidable trace amounts, and their individual contents are less than 500 ppm.

In the case of other embodiments, the crystallizable lithium aluminum silicate glass, or the product made of green glass made from it, or the product made of converted glass ceramic, preferably by mass relative to the oxide. Includes the following composition in%:
Li ₂ O 3.4 to <4
Al ₂ O ₃ 20.5-22.5
SiO ₂ 65-67.5
Na ₂ O + K ₂ O 0.4 to 1.0
MgO> 0.1 to <0.4
CaO> 0.1 to 0.8
CaO + BaO 0.7-1.8
SrO 0-0.5
BaO 0-1.5
CaO + SrO + BaO 0.8 ~ 2
ZnO 1.1-2.1
B ₂ O _{30 to 1}
TiO ₂ > 1.9 to <2.5
ZrO ₂ 1.6 ~ <2.0
SnO ₂ 0.2 to 0.33
TiO ₂ + ZrO ₂ + SnO ₂ 3.9-4.8
P ₂ O ₅ 0.01-0.8
Fe ₂ O ₃ > 0.01 to 0.018
Nd ₂ O ₃ 0.005-0.2
However, condition B2:
0.4 <MgO / SnO ₂ <1.7
Meet.

In order to further improve the economical production showing high light transmittance, slight color tone and slight scattering in a short ceramicization time, ceramicizable lithium aluminum silicate glass, or products produced from this, are used. Expressed in% by mass with reference to oxide,
Li ₂ O 3.4 to <4
Al ₂ O ₃ 20.5-22.5
SiO ₂ 65-67.5
Na ₂ O + K ₂ O 0.4 to 1.0
MgO> 0.1 to <0.4
CaO 0.28-0.8
CaO + BaO 0.7-1.8
SrO 0-0.5
BaO 0-1.5
CaO + SrO + BaO 0.8 ~ 2
ZnO 1.1-2.1
B ₂ O _{30 to 1}
TiO ₂ > 1.9 to <2.5
ZrO ₂ 1.6 ~ <2.0
SnO ₂ 0.2 to 0.33
TiO ₂ + ZrO ₂ + SnO ₂ 3.9-4.8
P ₂ O ₅ 0.01-0.8
Fe ₂ O ₃ > 0.01 to 0.018
Nd ₂ O ₃ > 0.01 to 0.15
Including
However, condition B2:
0.4 <MgO / SnO ₂ <1.7
Contains a particularly preferred composition that satisfies:

The composition described above can be interpreted as having the described components at least 98% by weight, in principle 99% by weight, of the total composition. For example, a large number of compounds of elements such as F, Cl, alkaline Rb, Cs, or elements such as Mn, Hf are common impurities in the case of mixed raw materials used in large-scale industrial use. Other compounds, such as compounds of elements W, Nb, Ta, Y, Mo, rare earths, Bi, V, Cr, Ni, may be contained in small proportions, generally in the ppm range.

The water content of crystallizable glass for the production of glass-ceramics is preferably 0.015-0.06 mol / l, depending on the selection of mixed raw materials and the process conditions at the time of melting. This corresponds to a β-OH value of 0.16 to 0.64 mm ^-1. During the conversion to glass-ceramic, the IR band considered for determining the water content changes. As a result, the β-OH value of the glass ceramic changes without changing the water content. This and the method for determining the β-OH value are described, for example, in European Patent Application Publication No. 1074520 (EP 1 074 520 A1).

Crystallizable glass is converted to glass-ceramic by a multi-step temperature process described below.

In the case of the first embodiment, the glass ceramic is transparent and contains a high quartz mixed crystal as the main crystal phase.

In order to minimize scattering, it is preferable to minimize the crystallite size. Indeed, this has traditionally required long nucleation and ceramicization times that are economically inconvenient. According to the composition according to the present invention, a glass ceramic in which the refractive indexes of the residual glass and the crystal phase are matched can be obtained. Therefore, a higher average crystallit size is possible for high quartz mixed crystals than for known compositions. Preferably, the high quartz mixed crystal of the glass ceramic exhibits an average crystallit size of at least 30 nm after ceramicization. An average crystallit size greater than 35 nm is particularly preferred. A preferred upper limit based on the increased scattering is an average crystallit size of less than 50 nm.

The crystal phase ratio of the high quartz mixed crystal of the glass ceramic is preferably at least 65% by mass, and preferably at most 80% by mass. This range is preferred to obtain the desired mechanical and thermal properties of the glass ceramic.

For a transparent glass ceramic having a thickness of 4 mm, the light transmittance (luminance) Y is more than 82%, preferably more than 83%, and particularly preferably more than 84%. The color tone c ^* is at most 5.5, preferably less than 4.5, and particularly preferably less than 4.

Measurements of scattering (English: haze) by ASTM D1003-13 are preferably less than 2.5%, preferably less than 2%, particularly preferably 1.5, for a 4 mm thick polished sample of LAS glass ceramic. Produces a haze value of less than%. The transparent glass-ceramics according to the invention therefore do not exhibit visually disturbing light scattering; thereby the object and the line of sight of the illuminated display are not altered. The display on the lower part of the glass-ceramic plate is thereby clear, the contours are clear and can be seen without fogging.

The characteristics of the glass ceramics according to the invention are preferably based on a defined composition combination that matches the composition of the green glass, from this composition, 300 minutes as described in the methods and examples according to the invention. In less than an overall period, the rapid ceramicization adapted results in a glass ceramic.

The thermal expansion of glass-ceramic is usually adjusted to a value of ^{0 ± 0.3.10-6} / K in the temperature range from room temperature to about 700 ° C. However, negative values are also shown to be preferred for color optimization, as a low MgO content and an extended composition range exhibiting condition B1 are acceptable. Thermal expansion coefficient alpha _20/700 is <- 0.25 is preferably from · 10 ^-6 / K, <- particularly preferably from 0.32 · 10 ^-6 / K. The coefficient of thermal expansion α _20/700 is greater than −0.6 ・ 10 ^-6 / K, preferably greater than −0.5 ・ 10 ^-6 / K, otherwise heating of glass-ceramic products. This is because the heat-induced stress is sometimes too high between the cold and hot regions. Negative expansion results in additional applications in the athermalisierung of optics without jeopardizing use in normal applications, because the difference from zero expansion is small.

In the case of other embodiments, the glass-ceramic contains a caretite mixed crystal as the main crystal phase. For economic reasons, from the same composition of crystallizable lithium aluminum silicate glass, both transparent glass ceramics containing high quartz mixed crystals as the main crystal phase and glass ceramics containing caretite mixed crystals as the main crystal phase are manufactured. It is preferable that it can be done. Depending on the embodiment of the ceramicization program, the choice of maximum temperature and retention time can ultimately result in an appearance from transparent to translucent to opaque. The average crystallit size is preferably greater than 60 nm. The crystal phase ratio is more than 60% by mass, preferably more than 80% by mass. The combination of different properties of both glass-ceramic aspects economically favorably accommodates a large number of applications.

The preferred shape for the glass-ceramics according to the invention or the products produced from them is the shape of the plate. This plate preferably exhibits a thickness of 2 mm to 20 mm, as it opens up important applications. Smaller thicknesses impair strength, and larger thicknesses are less economical due to the relatively high material requirements. This thickness is preferably selected to be 6 mm, except for applications as safety glass where high strength is an issue.

Suitable molding methods for the plate-like shape are, in particular, the roll method and the float method. A preferred molding method from the glass melt is through two rolls, as this method is advantageous on the basis of rapid cooling when the composition tends to surface crystallize. A preferred product according to the invention is a glass-ceramic plate by the roll method.

In this case, the glass-ceramic plate and preferably the product manufactured from now on may not only be finished flat, but may be three-dimensionally molded. For example, plates with bent edges, angled or curved edges may be used. The plate may be rectangular or may be present in other shapes, and in addition to flat areas, three-dimensionally shaped areas such as protrusions, or rolled rods, or ridges. It may include a plane as a portion or a recess. Geometry of the plate is performed during thermoforming, for example by a structured forming roll or by thermoforming post-stored on the starting glass, for example by a burner, an infrared irradiator or gravitational sagging. In the case of ceramicization, a supporting ceramic mold, such as a flat underlay, is used to avoid uncontrollable changes in geometry. Subsequent polishing on one or both sides is optionally possible where application is required.

The method according to the invention for producing crystallizable lithium aluminum silicate glass is:
a) Preparing mixed batches from industrial raw materials containing 20-80% by weight of cullet;
b) Melt this mixed batch and clarify it in a conventional device at a temperature below 1750 ° C .;
c) The glass melt is cooled and _{molded at a temperature near the processing temperature VA} , where the product of the desired shape is made, and d) cooled to room temperature in a slow cooling furnace, where the glass. Undesired stress within is characterized by being removed.

The mixing batch is formed so that after melting, a glass exhibiting the composition and properties according to the invention is produced. Melting is promoted by the addition of cullet, and a relatively high tank treatment amount can be obtained. The additional high temperature clarification device is omitted, and the maximum temperature of the glass melt in the melt tank is less than 1750 ° C, preferably less than 1700 ° C, as is acceptable in conventional techniques. During molding, preferably the flat-shaped glass strips are made by rolls and cooled to room temperature in a cooled reactor to relieve stress. From this glass strip, a plate of the desired size is produced with quality assurance for bulk and surface defects.

The next process step is ceramicization on a flat or three-dimensional, often ceramic underlay, which is preferably carried out in a roll oven. In the case of the method according to the invention for ceramicization, the heat-relaxed crystallizable starting glass is heated to a temperature range of about 680 ° C. within 3-60 minutes. The required high heating rate can be achieved in a roll oven on a large scale industrial basis. This temperature range of about 680 ° C. closely matches the conversion temperature of the glass. Above this temperature up to about 800 ° C. is a region showing a high nucleation rate. The temperature range of nucleation continues for a period of 10 to 100 minutes. After that, the temperature of the glass containing the crystal nuclei is raised to a temperature of 850 ° C. to 950 ° C. within 5 to 80 minutes, in which the high crystal growth rate of the high quartz mixed crystal phase stands out. This maximum temperature is maintained for up to 60 minutes. In this case, the structure of the glass-ceramic is homogenized and the optical, physical and chemical properties are adjusted. The resulting glass-ceramic is cooled to room temperature in less than 150 minutes in total. Cooling to preferably about 700 ° C. is carried out at a slow rate. Overall, the ceramicization time is less than 300 minutes, preferably less than 200 minutes, particularly preferably less than 150 minutes.

Preferably, the clear lithium aluminum silicate glass-ceramic containing a high quartz mixed crystal as the main crystal phase comprises a fireplace viewing window, fireproof glass, a combustion furnace viewing window (especially for thermal decomposition furnaces), and optionally a bottom coating. It is used as a cover in the cooking table, lighting field, as a safety glass in the form of an optionally bonded composite, as a carrier plate in a thermal process or as a fireplace interior.

In the case of fireplace viewing windows, it is desirable to have a good view of the combustion chamber and flames. In the case of countertops with a colored undercoat, the color of the undercoat should not be altered by the color of the glass-ceramic. For the above-mentioned use, a high value of light transmittance (luminance) Y according to the present invention and a slight color tone c ^* are preferable in relation to slight inconspicuous light scattering.

Apart from this, their use is also caused by clear lithium aluminum silicate glass-ceramics containing Cateite mixed crystals as the main crystal phase.

A colored countertop with the necessary closures from clear glass ceramic by applying an opaque coating on the top and / or bottom surface to prevent the technical assembly members under the countertop from being visible. Can be manufactured. The countertop is heated by a gas burner, irradiation heating or induction as usual.

The voids in the coating allow the installation of sensor areas, colored and white indicators, and displays.

It is possible to combine top and bottom coatings of a transparent glass-ceramic plate, and in this case also incorporate a partially transparent layer. Similarly, for example, signs for cooking areas can be applied. In this case, different known types of coatings such as organic or inorganic decorative paints, glow paints, silicone and solgel based paints, sputtering layers, metal layers, oxynitride layers, acid carbide layers and the like can be combined. .. In this case, these layers may be stacked and applied.

Also in the case of fireplace lookout windows or fireplace lookout windows, a coating, eg, an opaque cover on the edge of the glass window, may be desirable. The placement of the coating on the top or bottom of the glass-ceramic plate is done according to aesthetic requirements and special requirements for chemical and physical properties.

The display device includes an electronic element that emits light, for example, a light emitting diode, an OLED, an LCD, and a fluorescent display unit. It is possible to display all shapes, including point-shaped and planar-shaped displays including 7-segment displays. Since the emission spectrum of the radiating display may show a maximum value of one or more and a wide region, the display appears colored (eg, blue, purple, red, green, yellow, orange) or white. Based on the slight color tone c ^* of glass-ceramic, black-and-white displays and color displays or screens can also be manufactured without disturbing color tone modifications. The color tone of the display is optionally changed by a color filter or a colored layer applied to the lower surface. The hue of the display may be influenced by it, and may optionally be modified if the hue is changed by the glass ceramic. Similarly, control elements, sensor elements and adjustment / operation elements, such as capacitive or inductive elements, may be attached to the glass-ceramic plate.

Glass ceramics containing Cateite mixed crystals as the main crystal phase are in translucent or opaque form and are preferably used as countertops, carrier plates for thermal processes, cover plates in microwave ovens or interiors of combustion chambers. Will be done. In this case, the light transmittance is preferably less than 15%.

Another preferred use for both glass-ceramics is for use as a carrier plate or furnace interior, even if the main crystal phase contains a high quartz or cateite mixed crystal. In the ceramic industry, solar industry or pharmaceutical industry or medical industry, these glass ceramics are used as interiors of furnaces or chemicals that carry out chemical or physical coating methods, especially for manufacturing processes under high purity conditions. Suitable as a durable experimental equipment. Further, these glass ceramics are used as glass ceramic articles for high temperature application or extremely low temperature application, as furnace windows for combustion furnaces, as heat shields for blocking hot environments, reflectors, floodlights, projectors, beamers ( Beamer), as a cover for copiers, for applications where thermomechanical loads are applied, for example in a dark vision device, or as a cover for heater elements, especially as a cooking table, grill table or roasting table, as a white product. , As a radiator cover, as a wafer substrate, as an article with UV protection, as a fascia plate, or as a material for housing components of, for example, electronic devices, and / or a cover glass for IT such as mobile phones, laptops. As a scanner glass, or as a component for elastic protection.

Further preferred use of the main crystal phase comprises a glass-ceramic containing keatite mixed crystals as and 25 ° C. to 50 ° C. of thermal expansion is less than 0 ± 0.5 · 10 ^-6 / K article as precision members at room temperature, For example, as an Abstands normale or as a wafer stage, as a mirror support material for reflective optics such as in astronomy and LCD lithography or EUV lithography, or as a laser gyroscope. By selecting the ceramicization conditions, a glass ceramic exhibiting low thermal expansion at room temperature can be produced from the composition according to the present invention.

The transparent glass ceramics of the present invention are transparent, including slight color tones and high light transmittance, slight scattering, high chemical durability, mechanical strength, temperature durability, and these properties (for example, thermal expansion, Sufficiently meets the requirements for long-term stability with respect to changes in permeability, stress formation).

The transmittance curve of the glass ceramic of Example 10.

The present invention will be further illustrated based on the following examples.

In the only figure, the transmittance curve of the glass ceramic of Example 10 is shown.

Crystallizable glass was melted from a normal mixing batch in the glass industry at a temperature of 1620 ° C. for 4 hours. As this mixed raw material, lithium carbonate, aluminum oxide, aluminum hydroxide, aluminum metaphosphate, sand, sodium nitrate and potassium nitrate, magnesium oxide, lime, strontium carbonate, barium carbonate, zinc oxide, tin oxide, titanium oxide, zirconium silicate and This choice, in which neodymium oxide is used, makes it possible to meet both the requirements of an economical raw material with the requirement of a small impurity content for Fe, Ni, Cr, V, Cu, Mo, S colorable compounds. After melting the mixture in a crucible made of sintered silica glass, the melt is poured into a Pt / Rh crucible equipped with an inner crucible made of silica glass and homogenized with stirring at a temperature of 1600 ° C. for 60 minutes. It became. After this homogenization, the glass was clarified at 1640 ° C. for 2 hours. Subsequently, a member of about 120 × 140 × 30 mm ³ was cast and cooled to room temperature for the first time from 660 ° C. in a cooled reactor in order to relieve stress. The cast member was divided into the required sizes for testing and for ceramicization.

For some examples, Table 1 describes the composition and properties of crystallizable glass. In addition to the component content, important component relationships are also shown. Glasses 1 to 11 are glasses according to the present invention, that is, examples, and glasses 12 to 14 are comparative glasses, that is, comparative examples that are not of the present invention. The composition of the comparative glass is outside the scope of the present invention and exhibits the defects described in the manufacturing properties (melting temperature, processing temperature, devitrification resistance) and / or the color tone after conversion to glass-ceramic. Based on the typical impurities in the large industrial mixture used, this composition does not add up to exactly 100% by weight. Typical impurities are F, Cl, B, Mn, Rb, Cs, Hf, even if not intentionally introduced into this composition, which are typically less than 0.2% by weight. .. These impurities are often brought in through the raw materials for the components used, for example Rb and Cs via the Na or K raw materials, or Hf via the Zr raw materials.

The water content of the glass measured by IR spectroscopy is shown in Table 1.

During Table 1, the characteristics in the glassy state, transition temperature Tg [° C.], the processing temperature ^{_{V A [℃], 10 2}} - Temperature [° C.], the upper devitrification limit OEG [° C.], the devitrification resistance V _A -OEG and density [g / cm ³ ] are also listed. For the measurement of OEG, the glass is melted in a Pt / Rh10 crucible. Subsequently, the crucible is held at different temperatures within the machining temperature range for 5 hours. The highest temperature at which the first crystals of the glass melt form on the contact surface of the crucible wall determines OEG.

Table 2 relates to a glass ceramic produced from the glass of Table 1 and containing a high quartz mixed crystal as a main crystal phase. In this case, Examples 1 to 14 are Examples, and Examples 15 to 18 are Comparative Examples.
In Table 2, for each of the ceramicization programs shown, that is, Program 1 or Program 2, the characteristics of glass ceramic, that is, the spectral transmittance at 400 nm (standard light C, 2 °, 4 mm thickness) [%], Infrared transmittance at 1600 nm (standard light C, 2 °, 4 mm thickness) [%], thermal expansion between 20 ° C and 700 ° C [10 ^-6 / K], and high as measured by X-ray diffraction. The phase content [mass%] of the main crystal phase composed of quartz mixed crystals and the average crystallit size [nm] are shown. In Table 2, the light transmittance Y and the chromaticity coordinates L ^* , a ^* , b ^{* from the CIELAB system, the parameter c *} as a measure for color tone (saturation), and the haze value as a measure for scattering are shown. Is also shown.

Table 3 shows Examples 19 to 21 for glass ceramics produced from the glass 8 of Table 1 and containing a caretite mixed crystal as a main crystal phase. In addition to the parameters from Table 2, the tristimulus values for the measurements in the reflex are also shown. Furthermore, the appearance of the examples is qualitatively described.

In the case of the ceramicization program 1, it is heated to a temperature of 600 ° C. in a ceramicization furnace for 20 minutes. Further heated. The total time from room temperature to 680 ° C is 36 minutes. The temperature range from 680 ° C to 800 ° C is important for nucleation. Therefore, it is further heated. The total time from 680 ° C to 800 ° C is 64 minutes. In the case of this ceramicization program, a retention time of 30 minutes is introduced in the range of nucleation at a temperature of 750 ° C. Above about 800 ° C., the desired high quartz mixed crystal phase crystallization takes place. Within this range, the formation of the Fe / Ti colored complex and the Sn / Ti colored complex that hinder the formation is also strengthened. The total time from 800 ° C. to reaching the maximum temperature of 903 ° C. is 41 minutes. At a maximum temperature of 903 ° C. and a holding time of 10 minutes, the composition of crystals and residual glass is adjusted and the microstructure is homogenized. In this case, the chemical and physical properties of the glass ceramic are adjusted. Cooling is controlled to 700 ° C., and then the sample is quenched to room temperature by opening the furnace door; that is, in summary:

Ceramicization program 1 (ceramicization time 185 minutes):
a) Rapid heating in 20 minutes from room temperature to 600 ° C.
b) Temperature rise within 30 minutes from 600 ° C to nucleation temperature 750 ° C (heating rate 5 ° C / min), holding time 30 minutes,
c) Temperature rise within 61 minutes from 750 ° C to maximum temperature 903 ° C (heating rate 2.5 ° C / min), holding time at maximum temperature 10 minutes,
d) Within 34 minutes, cooling from 903 ° C to 700 ° C (at 6 ° C / min), then rapid cooling to room temperature.

The ceramicization program 2 is optimized for a short ceramicization time and a slight color tone c ^{* for the composition according to the invention.} The nucleation time may be further shortened as compared to Program 1 so that the scattering becomes less visually noticeable. It is heated to 720 ° C. in 25 minutes in an experimental furnace that allows for high heating rates. The total time to 680 ° C is 23.6 minutes. The temperature range from 680 ° C to 800 ° C is important for nucleation. The total time from 680 ° C to 800 ° C is 21.4 minutes. The time in this temperature range is chosen so that there is no visually disturbing scattering.
The heating rate is reduced above 800 ° C. to a maximum temperature of 890 ° C., because crystallization takes place within this range. The associated shrinkage process must not proceed too fast, as it can result in non-flatness of the product. The total time from 800 ° C. to the maximum temperature of 890 ° C. is 53 minutes, and the subsequent holding time is 10 minutes. The composition of the crystal and residual glass is adjusted and the microstructure is homogenized. The time in this temperature range is optimized for the good flatness of the glass-ceramic plate. Cooling is controlled to 600 ° C., and then the sample is quenched to room temperature by opening the furnace door; that is, in summary:

Ceramicization program 2 (ceramicization time 137 minutes):
a) Rapid heating in 25 minutes from room temperature to 720 ° C.
b) Temperature rise in 20 minutes from 720 to 800 ° C (heating rate 4 ° C / min),
c) Temperature rise from 800 ° C to 890 ° C in 53 minutes (heating rate 1.7 ° C / min), holding time at maximum temperature for 10 minutes,
d) Within 29 minutes, cooling from 890 ° C to 600 ° C (at 10 ° C / min), then rapid cooling to room temperature.

The additional ceramicization program 3 converted the ceramicizable glass of No. 8 (Table 1) to a glass ceramic containing a caretite mixed crystal as the main crystal phase. In the case of this program, the procedure was carried out up to 890 ° C. in the same manner as in Program 2, and then, unlike Program 2, the maximum temperature T _max was reached at a heating rate of 10 ° C./min without a holding time at 890 ° C. Heating was performed at a heating time of t _max (see the description in Table 3). From maximum temperature, it was cooled to 800 ° C. at 5 ° C./min and then rapidly to room temperature.

Transmittance measurements were performed on a 4 mm thick polished plate with standard light C at 2 ° using the instrument Perkin-Elmer Lambda 900. From the spectrum values measured in the range of 380 nm to 780 nm representing the visible light spectrum, the transmittance Y by DIN 5033 is calculated for the selected standard light type C and the observation angle of 2 °.
From this measurement, the chromaticity coordinates L ^* , a ^* , b ^* , and the parameter c ^* from the CIELAB system are similarly calculated. Reflection measurements were also made according to DIN 5033 with these parameters.

The scattering of glass-ceramics is determined by the measurement of cloudiness (English: haze). In this case, a double-sided polished sample having a thickness of 4 mm is measured with standard light C using a spectrophotometer (method B of standard ASTM D1003-13) for a spectral region of 400 to 800 nm. Scattering is characterized by haze values in Table 2.

^* 測定されず Table 1: Composition and properties of crystallizable glass

^* Not measured

Table 1 (continued): Composition and properties of crystallizable glass

^* 測定されず Table 2: Ceramicization conditions and characteristics of glass ceramics containing high quartz mixed crystals as the main crystal phase

^* Not measured

^* 測定されず Table 2 (continued): Ceramicization conditions and characteristics of glass ceramics containing high quartz mixed crystals as the main crystal phase

^* Not measured

Table 3: Ceramicization conditions and characteristics of glass ceramics containing cateite mixed crystals as the main crystal phase

Claims (20)

In crystallizable lithium aluminum silicate glass for producing transparent glass ceramics, the crystallizable lithium aluminum silicate glass is arsenic-free and antimony-free, except for unavoidable raw material impurities. And the following components (expressed in% by mass with reference to oxides):
Li ₂ O 3.4-4.1
Al ₂ O ₃ 20-22.5
SiO ₂ 64-68
Na ₂ O + K ₂ O 0.4 to 1.2
MgO 0.05 ~ <0.4
CaO 0-1
CaO + BaO 0.7-1.8
CaO + SrO + BaO 0.8 ~ 2
ZnO 0.3-2.2
TiO ₂ 1.8 to <2.5
ZrO ₂ 1.6 ~ <2.1
SnO ₂ 0.2 to 0.35
TiO ₂ + ZrO ₂ + SnO ₂ 3.8-4.8
P ₂ O ₅ 0~3
Fe ₂ O ₃ > 0.01 to 0.02
However, condition B1:
0.15 <MgO / SnO ₂ <1.7
Crystallizable lithium aluminum silicate glass, characterized by satisfying. The following components (expressed in% by mass based on oxides):
Li ₂ O 3.4 to <4
Al ₂ O ₃ 20.5-22.5
SiO ₂ 65-67.5
Na ₂ O + K ₂ O 0.4 to 1.0
MgO> 0.1 to <0.4
CaO 0.01-0.8
CaO + BaO 0.7-1.8
SrO 0-0.5
BaO 0-1.5
CaO + SrO + BaO 0.8 ~ 2
ZnO 1.1-2.1
TiO ₂ > 1.9 to <2.5
ZrO ₂ 1.6 ~ <2.0
SnO ₂ 0.2 to 0.33
TiO ₂ + ZrO ₂ + SnO ₂ 3.9-4.8
P ₂ O ₅ 0~3
Fe ₂ O ₃ > 0.01 to 0.018
Including, but condition B2:
0.4 <MgO / SnO ₂ <1.7
The crystallizable lithium aluminum silicate glass according to claim 1. The crystallizable lithium aluminum silicate glass according to claim 1 or 2, which comprises 0.005 to 0.2% by mass of Nd ₂ O _3. The crystallization according to any one of claims 1 to 3, wherein the condition of Nd ₂ O ₃ / Fe ₂ O ₃ > 2 is applied to the components Nd ₂ O ₃ and Fe ₂ O _3. Possible lithium aluminum silicate glass. The crystallizable lithium aluminum according to any one of claims 1 to 4, wherein the condition of Na ₂ O / K ₂ O> 2 is applied to the components Na ₂ O and K _{2 O.} Silicate glass. The crystallizable lithium aluminum silicate glass according to any one of claims 1 to 5, wherein the CaO ratio is at least 0.28% by mass. The crystallizable lithium aluminum silicate glass according to any one of claims 1 to 6, wherein the condition (CaO + BaO) / SrO> 3 is applied to the components CaO, BaO and SrO. .. The crystallizable lithium aluminum silicate glass according to any one of claims 1 to 7, wherein the P ₂ O _{5 ratio is 0.01 to 1.5% by mass.} The following components (expressed in% by mass based on oxides):
Li ₂ O 3.4 to <4
Al ₂ O ₃ 20.5-22.5
SiO ₂ 65-67.5
Na ₂ O + K ₂ O 0.4 to 1.0
MgO> 0.1 to <0.4
CaO> 0.1 to 0.8
CaO + BaO 0.7-1.8
SrO 0-0.5
BaO 0-1.5
CaO + SrO + BaO 0.8 ~ 2
ZnO 1.1-2.1
B ₂ O _{30 to 1}
TiO ₂ > 1.9 to <2.5
ZrO ₂ 1.6 ~ <2.0
SnO ₂ 0.2 to 0.33
TiO ₂ + ZrO ₂ + SnO ₂ 3.9-4.8
P ₂ O ₅ 0.01-0.8
Fe ₂ O ₃ > 0.01 to 0.018
Nd ₂ O ₃ 0.005-0.2
Including, but condition B2:
0.4 <MgO / SnO ₂ <1.7
The crystallizable lithium aluminum silicate glass according to any one of claims 1 to 8, wherein the glass satisfies the above conditions. The following components (expressed in% by mass based on oxides):
Li ₂ O 3.4 to <4
Al ₂ O ₃ 20.5-22.5
SiO ₂ 65-67.5
Na ₂ O + K ₂ O 0.4 to 1.0
MgO> 0.1 to <0.4
CaO 0.28-0.8
CaO + BaO 0.7-1.8
SrO 0-0.5
BaO 0-1.5
CaO + SrO + BaO 0.8 ~ 2
ZnO 1.1-2.1
B ₂ O _{30 to 1}
TiO ₂ > 1.9 to <2.5
ZrO ₂ 1.6 ~ <2.0
SnO ₂ 0.2 to 0.33
TiO ₂ + ZrO ₂ + SnO ₂ 3.9-4.8
P ₂ O ₅ 0.01-0.8
Fe ₂ O ₃ > 0.01 to 0.018
Nd ₂ O ₃ > 0.01 to 0.15
However, condition B2:
0.4 <MgO / SnO ₂ <1.7
The crystallizable lithium aluminum silicate glass according to any one of claims 1 to 9, wherein the glass satisfies the above conditions. ^{· 10 2} − temperature below 1770 ° C and / or • Machining temperature _VA up to 1330 ° C and / or • Devitrification upper limit OEG at least 10 ° C lower than _{said machining temperature VA}
The crystallizable lithium aluminum silicate glass according to any one of claims 1 to 10. A glass ceramic converted from the lithium aluminum silicate glass according to any one of claims 1 to 11. The glass ceramic according to claim 12, wherein the glass ceramic contains a high quartz mixed crystal as a main crystal phase. The glass ceramic according to claim 13, wherein the glass ceramic exhibits a light transmittance Y of more than 82% and / or a color tone c ^{* of up to 5.5 with a thickness of 4 mm.} Claimed for a thickness of 4 mm, characterized by visually inconspicuous scattering with a haze value <2%, a light transmittance of more than 82%, and a color tone c ^* of up to 5.5. Item 13. The glass ceramic according to item 13. The glass ceramic according to claim 12, wherein the glass ceramic contains a caretite mixed crystal as a main crystal phase. The glass ceramic according to any one of claims 12 to 16, wherein the glass ceramic exists in the form of a plate having a thickness of 2 mm to 20 mm. Process:
a) Prepare mixed batches of industrial raw materials containing 20-80% by weight of cullet;
b) Melt the mixed batch and clarify it in a normal apparatus at a temperature below 1750 ° C .;
c) The glass melt is cooled and _{molded at a temperature near the processing temperature VA} , and d) It is cooled to room temperature in a slow cooling furnace, according to any one of claims 1 to 11. The method for producing a crystallizable lithium aluminum silicate glass according to the above method. Next program for ceramicization:
a) Raise the temperature of crystallizable glass to a temperature range of about 680 ° C within 3-60 minutes;
b) Raise the temperature of the crystallizable glass within the temperature range of 680-800 ° C. for nucleation over a period of about 10-100 minutes;
c) Raise the temperature of the glass containing the crystal nuclei within the temperature range of a high crystal growth rate of 850 to 950 ° C. within 5 to 80 minutes;
d) Keep within the temperature range of the maximum temperature of 850-950 ° C. for up to 60 minutes, where crystals of the high quartz mixed crystal type grow on the crystal nuclei, and then;
e) The glass ceramic obtained is carried out by rapidly cooling to room temperature in less than 150 minutes, wherein the ceramicization of the glass exhibits an overall period of less than 300 minutes. The method for producing a glass ceramic according to any one of 13 to 15. As a fireproof glass, as a fireplace viewing window, as a combustion furnace viewing window, as a cooking table with a bottom coating in some cases, as a cover in the lighting field, as a safety glass in the form of an optionally bonded composite, a carrier plate in a thermal process. Alternatively, use of the article containing the glass-ceramic plate according to claim 17 as a furnace lining.

Images