JP2013087054A - X-ray opaque barium-free glass and use of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide BaO-free and PbO-free X-ray opaque glass which is particularly suitable as dental glass and optical glass and has excellent chemical resistance.SOLUTION: The BaO-free and PbO-free X-ray opaque glass in which impurities are removed at best: is an SiO-AlO-SrO-RO system added with LaOand ZrO; comprises, in mass in terms of oxide, 55-75% SiO, 0-9% BO, 0.5-4% AlO, 0-2% LiO, 0-7% NaO, 0-9% KO, 0-15% CsO, 4-17% SrO, 0-11% CaO, 0-<3% MgO, 1-<11% ZrO, 1-10% LaO, 0-4% SnO, 0.5-12% LiO+NaO+KO and ≥10% SrO+CsO+LaO+SnO+ZrO, has a refractive index nof 1.50-1.58; and has an aluminium equivalent thickness of at least 300%.

Description

  The present invention relates to barium-free and lead-free radiopaque glasses and their use.

In the dental field, polymer-based dental compositions are increasingly used for dental restorations. These polymer-based dental compositions usually comprise an organic resin matrix and various inorganic fillers. Inorganic fillers mainly consist of glass powder, (glass) ceramics, silica or other crystalline substances (eg YbF ₃ ), sol-gel materials or Aerosil®, and as fillers Added to the polymer base composition.

  The use of polymer-based dental compositions is intended to avoid the possible harmful side effects of amalgam and to achieve an improved aesthetic impression. Depending on the choice of polymer-based dental compositions, they can be used for various dental restorations, for example for tooth filling, and for parts such as crowns, bridges and inlays, onlays, etc. Can also be used for fasteners.

  Such fillers are intended to minimize shrinkage caused by polymerization of the resin matrix during curing. For example, strong adhesion between the tooth wall and the filling can lead to tooth wall failure due to excessive polymerization shrinkage. If the adhesion is insufficient, excessive polymerization shrinkage can lead to the formation of peripheral cracks between the tooth wall and the filling, which can promote secondary caries. Furthermore, the filler must meet specific physical and chemical requirements.

  The filler must be processed to produce a very fine powder. The finer the powder, the more uniform the appearance of the filling. At the same time, the glazing of the filling is improved, which results in improved wear resistance and thus greater durability of the filling due to the reduction of the surface area that can be attacked. In order to allow the powder to be easily processed, it is also desirable that the powder does not agglomerate. This undesirable effect occurs especially in the case of fillers produced by the sol-gel process.

  Furthermore, it is advantageous if the filler is coated with a functionally treated silane, as it makes formulation of the dental composition easier and improves the mechanical properties. In this case, the surface of the filler particles is usually at least partially coated with primarily functionally treated silane.

  In addition, the whole of the polymer-based dental composition, and therefore also the fillers, should be in good harmony with the natural tooth material as much as possible in their refractive index and color, thereby ideally around It cannot be distinguished from healthy tooth material. The very small particle size of the ground filler also plays a role in this aesthetic criteria.

  Also, in order to ensure sufficient thermal shock resistance for dental restoration treatment, it is present as a filler in a polymer-based dental composition and its use range, that is, usually between −30 ° C. and + 70 ° C. It is also important that the thermal expansion of the entire system consisting of the glass material to be matched with that of the natural tooth material. An excessively large temperature change can also form cracks between the polymer-based dental composition and the surrounding tooth material, which can give a suitable attack point for secondary caries. In general, fillers with a very low coefficient of thermal expansion are used to compensate for the large thermal expansion of the resin matrix.

  The good chemical resistance of fillers to acids, alkalis and water, and good mechanical stability under load, for example due to chewing action, can also contribute to a long service life for tooth restoration means. The filler should be resistant to tooth treatment with fluoride as well.

For patient treatment, it is also absolutely necessary to be able to see the dental restoration means on the X-ray image. Since the resin matrix is generally invisible in the X-ray image, the filler must provide the necessary X-ray absorption. This type of filler that absorbs X-ray radiation well is said to be radiopaque. Filler constituents, such as certain components or additives of glass, generally contribute to radiopacity. Additives such as these are also known as radiopaque agents. X-ray opaque agent widely used is YbF _3, it can be added in divided form of crystals.

  According to DIN ISO 4049, the radiopacity of dental glasses or materials has been reported as Aluminum equivalent thickness (ALET) in relation to the X-ray absorption of aluminum. ALET is the thickness of an aluminum sample that exhibits the same absorption as a 2 mm thick sample of the material being tested. Thus, an ALET of 200% means that a glass plate with a 2 mm thick parallel surface will produce approximately the same X-ray attenuation as a 4 mm thick aluminum plate. Similarly, an ALET of 500% means that a glass plate with a 2 mm thick parallel surface will produce approximately the same X-ray attenuation as a 10 mm thick aluminum plate.

  Since the polymer-based dental composition used is usually introduced from a cartridge into a cavity and cast in the cavity, it should often be thixotropic when uncured. This means that the viscosity decreases when pressure is applied, but is dimensionally stable when no pressure is applied.

  Among polymer-based dental compositions, a further distinction should be made between dental cements and composites. For example, in the case of dental cements, also known as glass ionomer cements, the chemical reaction of the filler with the organic matrix results in hardening of the dental composition, and as a result, the reactivity of the filler is dental. It affects the curing properties of the compositions and thus their processability. This often includes curing processes that can be preceded by free radical surface curing, for example under the action of ultraviolet light. Glass can serve as a filler that causes or participates in a chemical reaction, or an inert particulate material that would otherwise not participate in the reaction. The chemical reaction is then triggered by further fillers that are also present in the glass ionomer cement.

  On the other hand, composites, also known as filled composites, further comprise a chemically very inert filler. This is because their curing behavior is determined by the constituents of the resin matrix itself and thus early, and the chemical reaction of the filler and / or particulate material is often undesirable here.

  Because glasses represent a class of materials that have a wide range of properties for their various compositions, they are often used as fillers for polymer-based dental compositions. Other uses as a dental material in pure form or as a component of a mixture are for example cosmetics for inlays, onlays, crowns and bridges, materials for artificial teeth, or prosthetic, antiseptic and / or preventive dentistry It is possible for other materials for treatment as well. Such glass used as a dental material is generally called dental glass (dental glass).

  Apart from the properties of dental glass described above, it is also desirable that dental glass does not contain barium oxide (BaO) and does not contain toxic lead oxide (PbO) due to possible adverse health effects. .

Furthermore, it is likewise desirable for dental glass to contain zirconium oxide (ZrO ₂ ) as a component. ZrO ₂ is a material widely used in the dental and optical technical fields. ZrO ₂ is very biocompatible and insensitive to temperature fluctuations. It is used for many types of dental care in the form of crowns, bridges, inlays, operational tasks and implants.

  Thus, dental glass is a particularly high quality glass. Such glasses can also be used in optical applications, particularly those that benefit from the radiopacity of the glass. X-ray opacity means that the glass absorbs electromagnetic radiation in the region of the X-ray spectrum, so that such glass simultaneously acts as a filter for X-rays. Sensitive electronic components can be damaged by X-rays. In the case of an electronic image sensor, the transmission of the X-ray dose may, for example, damage the corresponding area of the sensor, or produce an undesirable sensor signal that can be perceived as, for example, an image and / or noise pixel fault. obtain. Thus, in certain applications, it is necessary, or at least advantageous, to protect electronic components from X-ray irradiation by filtering them out of the spectrum of incident electromagnetic radiation with suitable glass.

A number of dental glasses and other optical glasses with similar optical positions or comparable chemical compositions have been described in the prior art, but these glasses have considerable disadvantages in production and / or use . In particular, many glasses have a relatively large proportion of fluoride and / or Li ₂ O, which evaporate very easily during melting and remelting, resulting in an accurate setting of the glass composition. Make it difficult.

US Pat. No. 5,976,999 (Patent Document 1) and US Pat. No. 5,827,790 (Patent Document 2) relate, inter alia, to glassy ceramic compositions used as dental porcelain. CaO and Li ₂ O must be present in amounts of at least 0.5% and 0.1% by weight, respectively. Apart from the two main components from the group consisting of ZrO ₂ , SnO ₂ and TiO _2, an amount of CaO of at least 0.5% by weight appears to be essential therein. These components produce an increased refractive index _nd and only a low radiopacity. In these two documents, the glass must also contain at least 10% by weight of B ₂ O ₃ . The relatively high B ₂ O ₃ proportion combined with an alkali metal content of at least 5% by weight or at least 10% by weight results in the glass being unacceptably damaged and thus these glasses. Is not suitable for dental glass.

A chemically inert dental glass for use as a filler in a composite is the subject matter of German Patent Application DE 198 49 388 A1. The proposed glass must contain a significant content of ZnO and F. These can lead to a reaction with the resin matrix, which can also affect their polymerization properties. Furthermore, the SiO ₂ content is limited to 20-45% by weight so that the described glass can contain sufficient radiopacifier and F.

  International Publication WO 2005/060921 A1 (Patent Document 4) describes glass fillers that are said to be particularly suitable for dental composite materials. This contains 9 to 20 mol% of alkali metal oxide. The purpose of this document is to provide glass particles whose alkali metal ion concentration around the particles is lower than the alkali metal ion concentration between them. This means that the glass described is not chemically resistant, otherwise this concentration range cannot be achieved. The required low chemical resistance can be considered to be achieved by the above proportion of alkali metal in the starting glass.

European patent EP 0886066 B1 describes an alkali metal silicate glass that serves as a filler for dental materials. An Al ₂ O ₃ content of at least 5% by weight increases the viscosity of glasses with a high SiO ₂ content and thus leads to a very high melting temperature. In addition, the glass must contain fluorine. However, during glass melting, fluorides tend to evaporate easily, which makes it difficult to set the glass composition accurately and leads to inhomogeneities. Furthermore, in this system, the proportion of the component CaO that imparts radiopacity to the glass is 0.5 to 3% by weight, in order to achieve the desired radiopacity with an ALET of at least 300%. Is too low.

German patent application DE 44 43 173 A1 relates to a high zirconium glass having a ZrO ₂ content of more than 12% by weight and containing other oxides. Such fillers are too reactive, especially for very recent epoxy-based dental compositions that can cure too quickly and uncontrollably. This amount of zirconium oxide tends to be devitrified. This probably causes phase segregation with nucleation and subsequent crystallization. Furthermore, such glasses can only be produced with a high alkali metal content in order to ensure a melting temperature that is not too high and does not overstress the melting apparatus. However, such a high alkali metal content results in the disadvantage of the low chemical resistance of the glass.

  German patent application DE 199 45 517 A1 describes high-zirconium glasses which likewise give rise to the same problems associated with the glasses of said document in dental applications.

Japanese Patent Laying-Open No. 2004-002062 (Patent Document 8) discloses a glass substrate for a flat screen display. The disclosed glass mainly contains SrO with BaO and also contains a high proportion of Al ₂ O ₃ and MgO. In order to ensure the fusibility of the glass, the components Al ₂ O ₃ , SrO, BaO and MgO are necessary as a network conversion agent. These glasses are also not considered for use as dental glasses because they can contain BaO, or none of the low BaO variants are close to the desired radiopacity. Because. Apart from that, the Al ₂ O ₃ content leads to an increase in the viscosity of the high SiO ₂ glass, thus requiring a high melting temperature for production. The high content of MgO is disadvantageous in dental use glasses, which should have a low refractive index and at the same time a high radiopacity. MgO is other alkaline earth metal oxides CaO, but does not increase the X-ray opacity to the same extent as SrO and BaO, its presence has been known to increase the primarily refractive index n _d, therefore, It may be difficult to achieve the desired balance of low refractive index and high radiopacity.

  All the glasses mentioned in the prior art are hardly weatherable, are too reactive and / or are not radiopaque or contain components that impair the environment and / or health Either.

US Pat. No. 5,976,999 US Pat. No. 5,827,790 German patent application DE 198 49 388 A1 International Publication WO 2005 / 060921A1 European patent EP 0886066 B1 German patent application DE 44 43 173 A1 German patent application DE 199 45 517A1 JP 2004-002062 A

An object of the present invention are barium has a relatively low refractive index n _d of from 1.50 to 1.58 - to provide a free X-ray opaque glasses - free and lead. Glass should be suitable as dental glass and as optical glass and should be low cost to manufacture, nevertheless it should be of high quality, compatible with the body, passive It should be suitable for active tooth protection and should have excellent properties in terms of processability, the binding behavior of the surrounding polymer matrix and long-term stability and strength. In order to meet the demands on recent tooth treatment and dental technology, the glass according to the invention should also have very good chemical resistance.

Furthermore, the glass base matrix according to the invention allows an optimal color trajectory in order to be able to harmonize with the color of the teeth and / or in the case of optical applications to allow a transmission spectrum of electromagnetic radiation. At best, except for impurities, it should not contain coloring components such as Fe ₂ O ₃ , CoO, NiO, CuO. Furthermore, the glass should not contain secondary glass phases and / or color imparting particles that cause scattering or likewise change the color impression. One or more other glass phases reduce the stability of the glass.

In order to achieve the above object, according to the present invention, the following components are expressed in mass% on an oxide basis:
SiO ₂ 55~75%,
B ₂ O ₃ 0-9%,
Al ₂ O ₃ 0.5~4%,
Li ₂ O 0-2%,
Na ₂ O 0-7%,
K ₂ O 0~9%,
Cs ₂ O 0~15%,
SrO 4-17%,
CaO 0-11%,
MgO 0- <3%,
ZrO ₂ 1- <11%,
La ₂ O ₃ 1-10%,
SnO ₂ 0-4%,
_{Li 2 O + Na 2 O +} K 2 O 0.5~12%,
SrO + Cs ₂ O + La ₂ O ₃ + SnO ₂ + ZrO ₂ ≧ 10%
Containing not contain BaO and PbO at best remove impurities, X-rays opaque glass having an aluminum equivalent thickness refractive index _{n d} and at least 300% of 1.50 to 1.58 is provided.

  Furthermore, according to the present invention, their use as fillers in glass powders, dental glasses, especially dental restoration composites, fillers or inert particulate materials in glass / ionomer / cement, X-ray resistance in dental compositions. Permeants, use as optical elements, use as cover glass and / or substrate glass for electronic components, display technology, photovoltaic cells, OLED, biochemical applications, lamp glass, target materials in PVD processes, glass fiber Applications in various fields are also provided such as core glass and / or clad glass, optical waveguides, materials for embedding radioactive materials, container materials for packaging pharmaceuticals, and use as reinforcements in composite materials. Preferred embodiments and applications are indicated in the dependent claims.

The glass of the present invention has a refractive index _{n d} of from 1.50 to 1.58. It therefore matches very well with the dental polymers and / or epoxy resins available in this refractive index range, and as a result, makes an aesthetic demand for the natural appearance required for dental glass / polymer composites with respect to the natural appearance. Fulfill.

The glasses of the present invention achieve the properties of barium and / or lead-containing dental glasses with respect to the desired X-ray absorption without the use of barium and lead and advantageously other health-prone substances. Here, the term “... Free” means that these components are not present except at most inevitable impurities which may be caused by, for example, air pollution and / or impurities in the raw materials used. However, even glass contamination with undesirable materials should generally not exceed 100 ppm, preferably 50 ppm or less for Fe ₂ O ₃ , 30 ppm or less for PbO, 5 ppm or less for As ₂ O ₃ , Sb ₂ Should be 20 ppm or less for O ₃ and 100 ppm or less for others. BaO is always closely related to SrO in the raw material. Depending on the purity of the SrO raw material, 0.37% by weight or less of BaO can be present in the glass of the present invention. These limits are encompassed by the expression "free at best, excluding impurities". Of course, it is particularly preferred that the undesirable substances mentioned above are not completely present in the glasses of the invention.

X-ray absorption, and thus X-ray opacity, according to the invention is mainly determined by the components Cs ₂ O and / or La ₂ present in the SrO content and also in a combined amount of 10% by weight or more in the glass of the invention. Achieved with O ₃ and / or SnO ₂ and / or ZrO ₂ . In contrast to earlier dental glasses that attempted to achieve radiopacity with a high content of ideally superabsorbent components, the radiopacity according to the invention is preferably X This is achieved by an appropriate combination of these components effective for radiopacity. In this way, particularly rigorous demands made on the optical properties of the glass and also very good chemical resistance can be achieved. The total content of SrO and further components Cs ₂ O and / or La ₂ O ₃ and / or SnO ₂ and / or ZrO ₂ is preferably at least 11% by weight, in particular 12% by weight, particularly preferably at least 15 % By mass.

  SrO is always present in the glass of the present invention. Its content is 4 to 17% by mass. A suitable range is 4 to 16% by mass, more preferably 5 to 15% by mass, and particularly preferably 6 to 14% by mass. According to the present invention, in combination with other radiopaque agents, SrO ensures good radiopacity of the glass. In the region of 65 keV operating voltage, the X-ray absorption spectrum of SrO in glass is sub-optimal in the range of conventional tungsten X-ray tubes, but surprisingly combinations with the other materials described here It has been found that very good radiopacity can be achieved.

The glasses according to the invention have an aluminum equivalent thickness (ALET) of at least 300%, preferably at least 350%, particularly preferably at least 390%. This means that a glass plate made of the glass of the present invention and having a parallel surface and a thickness of 2 mm produces approximately at least the same X-ray attenuation as an aluminum plate having a thickness of 6 mm. .
Other effects of the present invention will become more apparent from the following description.

As a base component, the glass of the present invention contains SiO ₂ in a proportion of 55 to 75% by mass as a glass forming component. A higher SiO ₂ content disadvantageously tends to result in a high melting temperature and furthermore the desired radiopacity cannot be achieved. Content less than this can adversely affect chemical resistance. A preferred embodiment of the glass according to the invention is that the SiO ₂ content is 56-74% by weight, particularly preferably> 59-70% by weight.

B ₂ O ₃ is merely an optional component in the glass of the present invention and can exist in the range of 0 to 9% by mass. B ₂ O ₃ is provided as a flux. In addition to lowering the melting temperature, the use of B ₂ O ₃ simultaneously improves the crystallization stability of the inventive glass. A content higher than about 9% by weight is not recommended in this system in order not to harm the good chemical resistance. B ₂ O ₃ is preferably used in a proportion of 0 to 7% by mass, particularly preferably 0 to 4% by mass. When B ₂ O ₃ is present in the glass of the present invention, a small amount of 0.5% by weight or more to the glass is also avoided to avoid unwanted scattering in segregated areas similar to the Tyndall effect. It is preferable to introduce an alkali metal oxide.

In the glass of the present invention, Al ₂ O ₃ must be present in the range of 0.5 to 4% by mass. Al ₂ O ₃ inter alia enables good chemical resistance. However, the Al ₂ O ₃ content should not exceed about 4% by weight in order not to increase the viscosity of the glass to a rate that makes the glass difficult to melt, especially in the hot working range. . The upper limit of the Al ₂ O ₃ content is preferably 3.5% by mass, more preferably only 3% by mass, particularly preferably only 2% by mass.

Alkali metal oxides can reduce the chemical resistance of the glass, but on the other hand are necessary to allow the glass to melt anyway. According to the invention, the total amount of alkali metal oxides Li ₂ O and / or Na ₂ O and / or K ₂ O is 0.5-12% by weight, preferably 0.5-11% by weight, more preferably Is 2 to 10% by mass, particularly preferably 3 to 9% by mass. The present invention balances these alkali metals in the specified range. In particular, in the glasses of the present invention, alkali metal oxides from the group consisting of Li ₂ O and / or Na ₂ O and / or K ₂ O are desirable, which is similar to the segregation of the glass matrix and hence the Tindall effect. Prevents no scattering. Accordingly, the alkali metal oxide is present in a total amount of at least 0.5% by weight. In addition, alkali metal oxides along with B ₂ O ₃ help melt the glass at acceptable temperatures. However, in order to be able to achieve the very high resistance of the glass of the invention, the alkali metal oxide should not exceed a maximum of 12% by weight.

More specifically, the content of these alkali metal oxides is, according to the invention, Li ₂ O 0-2% by mass, preferably 0-1% by mass, particularly preferably 0- <1% by mass. It is. A very low proportion of Li ₂ O helps to achieve very good chemical resistance. For this reason, particularly highly preferred glasses are also, at best, free of Li ₂ O—free of impurities.

The content of Na ₂ O can be higher than the content of Li ₂ O. According to the invention, Na ₂ O is present in an amount of 0-7% by weight, preferably 0-5% by weight, more preferably 0-4% by weight, particularly preferably 0-3% by weight.

K ₂ O may be present in the glass of the present invention in an amount of 0-9% by weight. A preferable range is 0 to 8% by mass, more preferably 0 to 7% by mass, and particularly preferably 0 to 6% by mass. Li ₂ O, Na ₂ O and K ₂ O can particularly contribute to better melting of the glass containing SiO ₂ and ZrO ₂ .

Cs ₂ O likewise contributes to improving the melting properties, but according to the present invention it simultaneously increases the radiopacity and serves to adjust the refractive index in conjunction with other components. Is done. According to the present invention, in the glass according to the present invention, Cs ₂ O is 0 to 15% by mass, preferably 1 to 14% by mass, more preferably 2 to 13% by mass, particularly preferably 3 to 12% by mass. Present in quantity. The alkali metal Cs is more immobile in the glass base material than the alkali metals Li, Na, K and Rb. Therefore, the rate of leaching is lower than that of the alkali metal, and therefore the rate of damage to chemical resistance is lower.

  The glass of the present invention can contain a limited proportion of alkaline earth metals from the group consisting of CaO and MgO. The proportion of CaO is 0 to 11% by mass, preferably 0 to 10% by mass, more preferably 0 to 8% by mass, and particularly preferably 0 to 7% by mass. MgO is likewise optional and can be present in an amount of 0 to <3% by weight, preferably 0 to <2% by weight, particularly preferably 0 to <1% by weight. A particularly highly preferred embodiment provides a glass according to the invention which, at best, does not contain MgO except for impurities. As noted above, MgO can be disadvantageous in dental glasses that are intended to have a low refractive index and at the same time high radiopacity. MgO does not increase the radiopacity to the same extent as other alkaline earth metal oxides CaO, SrO and BaO because the X-ray absorption edge of MgO is much higher than the other three X-ray absorption edges. This is because it has only a small effect on the area of tungsten x-ray tubes used in the medical field. MgO simply increases the refractive index, thus making it more difficult to achieve a balance between low refractive index and high radiopacity.

Furthermore, the glass of the present invention must contain ZrO ₂ in a proportion of 1% by mass or more and less than 11% by mass. This zirconium content improves the mechanical properties, in particular in this case it improves the tensile and compressive strength and reduces the brittleness of the glass. Furthermore, this component makes a similar contribution to the radiopacity depending on the proportion of SrO in the glass. However, its too high content can lead to the glass becoming reactive, especially in dental polymer environments. On the other hand, the glass should be at least very inert, in particular with respect to the dental polymer in the composite material, for example it should not interfere with its polymerization behavior. The ZrO ₂ content is preferably 1% by mass or more and less than 10% by mass, preferably 2 to 9.5% by mass, particularly preferably 2 to 9% by mass.

The ZrO ₂ content should not be exceeded because ZrO ₂ is poorly soluble in silicate glass and therefore segregation can easily occur. In the case of an excessively high ZrO ₂ content, the segregation region that can be formed, especially in combination with a similarly high SiO ₂ content, acts as a center for scattering the light passing therethrough, similar to the Tyndall effect. In the case of dental glass, these scattering centers are detrimental to the aesthetic impression, which is why segregated glass is generally not desired in dental applications. Also, in optical glass, scattering centers generally have an adverse effect on transmission, and thus segregated glass is equally undesirable in most optical applications. Furthermore, segregated glass can lead to reduced resistance due to different compositional phases and thus different leaching properties.

La ₂ O ₃ is present in the glass of the present invention in an amount of 1 to 10% by mass. As mentioned above, La ₂ O ₃ ensures the radiopacity of the glass, optionally with SrO and ZrO ₂ and optionally with Cs ₂ O and / or optionally SnO ₂ . The La ₂ O ₃ content is preferably 2 to 8% by mass, more preferably 3 to 7% by mass, and particularly preferably 3 to 6% by mass.

Similar to Cs ₂ O, SnO ₂ can be present as an optional component in the glasses of the present invention in order to achieve high radiopacity with an ALET of at least 300%. This component has the advantage of not increasing the refractive index to the same extent as La ₂ O ₃ and / or Ta ₂ O ₅ . Thus, SnO ₂ also helps to set a low refractive index of 1.5 to 1.58 in combination with high radiopacity. It can therefore be present in the glass in an amount of 0-4% by weight. It is preferably present in the glass according to the invention in an amount of 0 to 3% by weight.

The glass of the present invention may optionally, at best remove impurities, CeO ₂ - free and TiO ₂ - is free. Due to their absorption in the UV range, CeO ₂ and TiO ₂ shift the UV edge of the glass so that an undesirable yellowish coloration is obtained.

In order to achieve a high radiopacity and correspondingly a particularly high value of the aluminum equivalent thickness, in a preferred embodiment of the glass according to the invention, SrO, Cs ₂ O, La ₂ O ₃ , ZrO present in the glass are used. The total amount of ₂ and / or SnO ₂ is> 18% by weight, preferably> 20% by weight, more preferably> 21% by weight, particularly preferably> 22% by weight.

In order to ensure that the glass does not decompose, the numerical value of the ratio of the SiO ₂ content to the ZrO ₂ content is preferably at least 6.5, particularly preferably greater than 7.

The glasses of the present invention preferably have WO ₃ and / or Nb ₂ O ₅ and / or HfO ₂ and / or Sc ₂ O ₃ and / or Y ₂ O ₃ and / or Yb ₂ O ₃ individually or desired In each case, it can optionally be further contained in an amount of 0 to 3% by weight, and Ta ₂ O ₅ can be optionally contained in an amount of 0 to 5% by weight in the desired combination.

The present invention also provides a glass of the present invention that is B ₂ O ₃ -free (excluding inevitable impurities at best).

  As described above, the glass of the present invention does not contain undesirable components BaO and PbO (excluding the above impurities at best). The addition of other substances harmful to the environment and / or health is also preferably avoided.

  In order to ensure particularly good melting properties of the glass, according to the invention, it is likewise specified that the total content of MgO and / or CaO and / or SrO is less than 17% by weight. If it is difficult to melt the glass, excessive stress is applied to the melting device, making it very difficult to melt the glass and generally it can no longer be produced economically.

  The glass transition temperature Tg of the glass according to the invention is preferably at least 570 ° C. Accordingly, the glass has high heat resistance and is suitable for other application fields, particularly the application fields described later.

The linear thermal expansion coefficient α _(20-300) measured in the temperature range from 20 ° C. to 300 ° C. of the glass of the present invention is preferably less than 7 × 10 ⁻⁶ / K. The low coefficient of thermal expansion, particularly when used as a polymeric filler material, allows the glasses of the present invention to compensate for the naturally high thermal expansion of the polymer. As a result, the polymer-containing dental composition has a thermal expansion that better matches the natural tooth material.

  As mentioned above, the glasses according to the invention are particularly resistant to chemical attack, i.e. they are particularly resistant to chemicals. They preferably have acid resistance S according to class 2 or better DIN 12116, alkali resistance L according to class 1 DIN ISO 695, and water resistant HGB according to class 2 or better DIN ISO 719. Tests for alkali resistance L and acid resistance S are much more desirable than the previously used test standards DIN ISO 10629 and ISO 8424, so that the glasses of the present invention are particularly improved in alkali resistance and acid resistance. It has sex.

  Similarly, the present invention defines the glass of the present invention to have a very good resistance to attack by NaF. The test method is described in more detail later in this specification in connection with the examples. This test aims to test the resistance of the glass to fluorine and / or fluoride. These materials can strongly attack the glass, but are often used by dentists, inter alia, for toothpaste materials and / or for fluorination and / or strengthening of healthy tooth materials.

  Thus, all the glasses of the present invention are characterized by very good chemical resistance, which results in a high inertness with respect to reaction with the resin matrix, and thus a very long service life of the entire dental composition. Bring.

  Furthermore, in a preferred embodiment of the present invention, the glass of the present invention preferably also does not contain any other components not claimed and / or described herein. This means that in such embodiments, the glass consists essentially of specified components. Here, the expression “consisting essentially of” means that other components may be present at most as impurities, but not intentionally added to the glass composition as individual components.

  However, the present invention also provides the glass of the present invention as a base for other glasses, in which case other components can be added up to 5% by weight to the glass of the present invention described above. In such a case, according to the present invention, the glass comprises at least about 95% by mass of the glass described above.

Needless to say, it is also possible to modify the color appearance of the glass by adding conventional oxides for this purpose. Oxides suitable for imparting color to the glass are known to those skilled in the art; examples include CuO and CoO, which for this purpose are preferably 0-0.5 wt. % Can be added. Furthermore, the glass can impart an antiseptic function by adding, for example, Ag ₂ O in an amount of 0 to 3% by mass.

  The present invention further includes a glass powder comprising the glass of the present invention. The glass powder is produced by known methods, for example as described in German Patent DE 41 00 604C1. The glass powder according to the present invention preferably has an average particle size of 50 μm or less, particularly preferably 20 μm or less. An average particle size of 0.1 μm can be achieved as the lower limit, and of course, an average particle size smaller than this is also included in the present invention. The glass powders described above can generally serve as starting materials for the use of the glasses of the invention as fillers and / or dental glasses.

  In a preferred embodiment, the surface of the glass powder is silanized by a conventional method. Silanization can improve the binding of inorganic fillers to the polymer matrix of polymer-based dental compositions.

As described above, the glass of the present invention can be suitably used as dental glass. Preferably, it is used as a filler in composites for dental restoration, particularly preferably as a filler for composites based on epoxy resins that require a substantially chemically inert filler. The present invention likewise provides the use of the glasses of the present invention as a radiopaque agent in dental compositions, in particular polymer-based dental compositions. The glass of the present invention are suitable, for example, replace the expensive crystalline X-ray opacifiers such as YbF _3. The glasses according to the invention are likewise suitable as fillers in glass, ionomers and cements and are used for their use. Similarly, the glass of the present invention can be used as an inert particulate material in glass ionomer cement. Particularly preferred is its use as an inert particulate material in polymer reinforced glass, ionomer cement. Polymer reinforced glass ionomer cements are a class of materials that have been available for only a few years, and they themselves exhibit a cement curing reaction that can take a very long time, so that they can be cured early. For this purpose, a resin base material such as the composite material described above is also included.

  Therefore, the glass of the present invention is suitably used for the production of a dental glass-polymer composite containing a dental polymer. Here, the dental polymer is preferably acrylate, methacrylate, 2,2-bis [4- (3-methacryloyloxy-2-hydroxypropoxy) phenyl] propane (bis-GMA), triethylene glycol methacrylate (TEGDMA), It is an ultraviolet curable resin based on urethane methacrylate (UDMA), alkanediol dimethacrylate or cyanoacrylate.

  The invention also encompasses the use of the glass of the invention as an optical element comprising the glass of the invention. For the purposes of the present invention, an optical element is a component that can be used for all objects, in particular for optical applications. These can be components through which light passes. Examples of such components are cover glasses and / or lens elements, but there are also supports for other components such as mirrors, glass fibers, etc.

  The cover glass is preferably used for protecting electronic components. Of course, these include optoelectronic components as well. The cover glass is usually in the form of a glass plate having a flat parallel surface, and preferably protects the electronic component from the influence of the surrounding environment. For example, electromagnetic rays such as light pass through the cover glass and the electronic component. Mounted on the electronic component to interact. Examples of such cover glasses are elements for the protection of electronic image sensors in optical caps, cover wafers in wafer level packages, cover glasses for photovoltaic cells and protective glasses for organic electronics. Still other uses for cover glasses are well known to those skilled in the art. Furthermore, for example, if the cover glass is provided at least in a region having an optical structure that can preferably take the form of a lens, it is also possible to integrate the optical function into the cover glass. The cover glass provided with the microlens is usually used as a cover glass for an image sensor of a digital camera, and the microlens usually collects light that strikes the image sensor obliquely on individual sensor elements (pixels). Needless to say, the glass of the present invention can be used as a substrate glass for an electronic component in which the electronic component is embedded in and / or applied to the substrate glass.

  Because of its optical properties, the glasses of the present invention can be used for optical applications as well. Support for substrate glass and / or cover glass and / or support for thin film photovoltaic module, for example in photovoltaic cells covering silicon-based photovoltaic cells and organic photovoltaic cells, and / or because they are very chemically inert Suitable for use as a material. The X-ray absorption of the glass of the present invention is particularly advantageous when using photovoltaic modules in space travel applications because it can be exposed, inter alia, to particularly intense X-rays outside the Earth's atmosphere. Furthermore, due to its high X-ray absorption properties, it can be used generally as an X-ray protective glass.

  The glasses according to the invention have also been found to be superior in application fields as cover glasses and / or substrate glasses for OLEDs (organic light emitting diodes) due to their properties. For example, due to its chemical resistance, undesirable interactions between the glass and the OLED material can be avoided or at least suppressed.

  The glasses according to the invention are also suitable for use as cover glasses and / or substrate glasses for biochemical applications, in particular for molecular sieve processes.

  Because of its high heat resistance, the glass of the present invention is suitable for use as a lamp glass, particularly in halogen lamps and / or fluorescent tubes and related buildings. When X-rays are generated by the light generation mechanism in the lamp, a particular advantage of the glass of the present invention is that it can protect the environment from X-rays.

  Furthermore, the present invention encompasses the evaporation of the glass of the present invention by physical processes and the deposition of the evaporated glass on a part. Such physical vapor deposition processes (abbreviation: PVD process) are known to the person skilled in the art and are described, for example, in German patent DE 102 22 964B4. In such a process, the glass of the present invention serves as a target to be evaporated. Parts deposited with the glass of the present invention can benefit from both the chemical resistance of the glass and its X-ray absorption.

Similarly, the glass of the present invention can also be used as a starting material for glass fibers. Here, the term “glass fiber” refers to all types of glass fibers, in particular fibers consisting only of a core, and so-called cores having at least one cladding that surrounds the core, preferably completely along its outer circumference. Clad fiber. In this case, the glass of the present invention can be used as a core glass and / or a clad glass. Within the composition range of the glass of the present invention, the refractive index n _d of the glass may be a core glass according to the present invention is set to have a higher refractive index than the cladding glass according to the present invention, therefore, the light core A so-called step index type fiber is obtained which is transmitted very efficiently as a result of total reflection at the cladding interface. The term also includes side light emitting (or side leakage) fibers as described, for example, in International Publication WO 2009/100834 A1.

  In addition, the glasses of the present invention are also suitable for safe temporary and / or permanent storage of radioactive waste, due to their high stability and, if desired, by their X-ray absorbance, and Furthermore, it is suitable as a base material for embedding radioactive substances.

  This glass is also advantageous for use as a container glass or for packaging pharmaceutical products. Due to the high resistance to the surrounding medium, the interaction with the contents can be virtually prevented.

  Due to its good chemical resistance, other fields of application are in particular the glasses according to the invention as composite reinforcements and / or as concrete reinforcements and / or as optical waveguide fibers embedded in concrete. The use of fiber.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, it cannot be overemphasized that this invention is not limited to the following Example.
Examples 1-19
Tables 1 to 3 show examples of the glass in the preferred composition range of the present invention. In addition, all the numerical values regarding a composition are the mass%.

  All ALET values (aluminum equivalent thickness) were determined by a method based on DIN ISO 4049, but using a digital X-ray apparatus. The resulting gray-scale values were further processed by image analysis software and X-ray absorption was then determined.

The glass described in each example was prepared as follows:
Weigh the raw material for the oxide without a fining agent and then mix thoroughly. The glass batch is melted at about 1580 ° C. in a discontinuous (batch type) melter and then clarified and homogenized. The glass can be cast at a casting temperature of about 1600 ° C. and can be processed as a ribbon or other desired dimensions. In large capacity continuous devices, the temperature can be lowered by at least about 100K.

  For further processing, the cooled glass ribbon was pulverized by methods known from German patent DE 41 00 604C1 to form glass powders having an average particle size of 10 μm or less. Glass properties were determined based on the glass mass that was not crushed into powder. All glasses exhibited excellent chemical resistance to acids, alkalis, water, and fluorine-containing materials such as NaF and NaF / acetic acid.

Tables 1 to 3 also show that the refractive index n _d , glass transition temperature Tg, linear thermal expansion coefficient α _{(20 to 300 ° C.) at} 20 to 300 ° C., and α _{(−30 to 70 °} C. at _{−30 to 70 ° C. )} Is shown. The latter is of particular interest when the glass of the present invention is used as a dental glass, because a temperature range of -30 to 70 ° C can occur during use.

  Further, Tables 1 to 3 show chemical resistances quantified by values obtained for acid resistance, alkali resistance, and water resistance of various glasses of the present invention. Here, S represents the acid resistance class according to DIN 12116, L represents the alkali resistance class according to DIN ISO 695, and HGB represents the water resistance class according to DIN ISO 719.

  Furthermore, in order to measure the excellent chemical resistance of the glasses according to the invention, more rigorous tests were carried out, in particular testing the resistance to fluorine and / or fluoride. Resistance to fluorine-containing components that are often performed in dentifrice materials and serve to fluorinate and / or strengthen healthy tooth materials were tested with NaF and NaF / acetic acid solutions as follows: 50% monomer, And production of composites from 50% silanized glass powder with an average particle size (d50) of 3 μm measured by laser light scattering (CILAS 1064L apparatus). The test sample is polished on both sides and exposed to a 0.001 molar NaF solution, and a 0.001 molar NaF solution and 4% acetic acid solution for 16 hours at a temperature of 37 ° C to 100 ° C. The surface of the polished sample is inspected by SEM (scanning electron microscope) before and after the resistance test.

  Very good samples showed no change. Good samples showed only slight interfacial cracks between the monomer and glass powder particles. Poor samples showed that glass particles were leached from the monomer matrix. Due to the expense of performing this test, the test results are not yet available for all variants of the glass according to the invention.

All the glasses shown in Tables 1 to 3 have a coefficient of thermal expansion α _(20-300) of less than 7 × 10 ⁻⁶ / K in the range of 20 to 300 ° C., and within the limits of the measurement accuracy of the analysis. Does not contain.

  Compared to the BaO-containing glass, the glasses shown in Tables 1 to 3 have at least as good radiopacity as that. In the example shown, ALET values of 399 to 763% are achieved.

Each example also, the refractive index n _d of the glass system of the present invention is to demonstrate that can be adapted to a desired without compromising ALET, can be adapted to the application, in particular application in the range of 1.53 to 1.56 ing. As a result, it can be advantageously used especially as a filler in dental compositions, but it is also advantageously used in other applications where purity, chemical resistance and heat resistance are required. be able to. Furthermore, it can be produced industrially with reasonable efforts.

Compared to the prior art, the glasses of the present invention have the further advantage of having refractive index and expansion coefficient adaptability and also constantly very good chemical stability in combination with efficient X-ray absorption.
The glasses of the present invention also melt relatively easily and can therefore be produced efficiently.

Claims (12)

The following components in terms of mass% on oxide basis:
SiO ₂ 55~75%,
B ₂ O ₃ 0-9%,
Al ₂ O ₃ 0.5~4%,
Li ₂ O 0-2%,
Na ₂ O 0-7%,
K ₂ O 0~9%,
Cs ₂ O 0~15%,
SrO 4-17%,
CaO 0-11%,
MgO 0- <3%,
ZrO ₂ 1- <11%,
La ₂ O ₃ 1-10%,
SnO ₂ 0-4%,
_{Li 2 O + Na 2 O +} K 2 O 0.5~12%,
SrO + Cs ₂ O + La ₂ O ₃ + SnO ₂ + ZrO ₂ ≧ 10%
The contained, does not contain BaO and PbO at best remove impurities, X-rays opaque glass having an aluminum equivalent thickness refractive index _{n d} and at least 300% of 1.50 to 1.58. The following components in terms of mass% on oxide basis:
SiO ₂ 56~74%,
B ₂ O ₃ 0-7%,
Al ₂ O ₃ 0.5~3.5%,
Li ₂ O 0-1%,
Na ₂ O 0~5%,
K ₂ O 0-8%,
Cs ₂ O 1~14%,
SrO 4-16%,
CaO 0-10%,
MgO 0- <2%,
ZrO ₂ 1- <10%,
La ₂ O ₃ 2-8%,
SnO ₂ 0-3%,
_{Li 2 O + Na 2 O +} K 2 O 0.5~11%,
SrO + Cs ₂ O + La ₂ O ₃ + SnO ₂ + ZrO ₂ ≧ 11%
The radiopaque glass according to claim 1, comprising: The following components in terms of mass% on oxide basis:
SiO _2> 59~70%,
B ₂ O ₃ 0-4%,
Al ₂ O ₃ 0.5~2%,
Li ₂ O 0- <1%,
Na ₂ O 0-3%,
K ₂ O 0-6%,
Cs ₂ O 3~12%,
SrO 6-14%,
CaO 0-8%,
MgO 0- <1%,
ZrO ₂ 2-9%,
La ₂ O ₃ 3-6%,
SnO ₂ 0-3%,
Li ₂ O + Na ₂ O + K ₂ O 3-9%,
SrO + Cs ₂ O + La ₂ O ₃ + SnO ₂ + ZrO ₂ ≧ 15%
The radiopaque glass according to claim 1 or 2, comprising: 4. The X-ray defect according to claim 1, wherein the total content of SrO, Cs ₂ O, La ₂ O ₃ , SnO ₂ and ZrO ₂ is> 18% in terms of mass% on an oxide basis. Transparent glass. The radiopaque glass according to any one of claims 1 to 4, wherein the content ratio of SiO ₂ and ZrO ₂ is SiO ₂ / ZrO ₂ ≥6.5. In addition, the following components in terms of mass% based on oxide:
WO ₃ 0~3%,
Nb ₂ O ₅ 0-3%,
HfO ₂ 0-3%,
Ta ₂ O ₅ 0-5%,
Sc ₂ O ₃ 0-3%,
Y ₂ O ₃ 0-3%,
Yb ₂ O ₃ 0-3%
The X-ray opaque glass as described in any one of Claims 1 thru | or 5 containing these. At most trace amounts except contains no B ₂ O ₃ and / or Li 2 _O and / or fluoride, and oxide content of ZnO in the criteria of claims 1 to 6 is less than 5 wt% The radiopaque glass as described in any one of Claims. The radiopaque glass according to any one of claims 1 to 7, which has a coefficient of thermal expansion α _(20-300) of less than 7 × 10 ^-6 / K.   9. An acid resistant S according to class 2 or better DIN 12116, an alkali resistance L according to class 1 DIN ISO 10695, and a water resistant HGB according to class 2 or better DIN ISO 719. The radiopaque glass according to one item.   A radiopaque glass comprising the radiopaque glass according to any one of claims 1 to 9 at a ratio of at least 95% by mass based on an oxide.   A glass powder comprising the radiopaque glass according to any one of claims 1 to 9. As dental glass and / or as filler in dental restoration composites and / or as filler or inert particulate material in glass ionomer cements and / or polymer-based dental compositions As radiopaque agents in objects and / or as optical elements and / or as cover glasses and / or substrate glasses of electronic components and / or as cover glasses and / or substrate glasses in display technology And / or as a cover glass and / or substrate glass in photovoltaic cells and / or as a cover glass and / or substrate glass for OLED and / or for cover chemistry and / or for biochemical applications Or as substrate glass and / or-as lamp glass and / or-PVD pro As a target material and / or as a glass fiber core glass and / or cladding glass and / or as an optical waveguide and / or as a material for embedding radioactive material and / or Use of the glass according to any one of claims 1 to 10 as a container material for packaging pharmaceuticals and / or as a reinforcement in composite materials.