ELEMENT COMPOSED OF GLASS DISPLAYING REDUCED ELECTROSTATIC CHARGING

Abstract

An element composed of glass displaying reduced electrostatic charging is provided. The element is suitable as a housing component for electronic elements, an element implantable in the human or animal body including glass tubes for reed switches or transponders and/or implants. The glass includes at least one alkali metal and/or an alkali metal oxide and has a surface. The concentration of at least one alkali metal and/or the alkali metal oxide increases from the surface in a direction of an interior of the element in such a way that a maximum concentration of the alkali metal and/or the alkali metal oxide occurs at a distance of not more than 60 nanometres, measured perpendicularly from the surface.

Claims

1. An element comprising: glass having a surface and interior, the glass comprising at least one alkali metal and/or an alkali metal oxide, wherein the glass has a concentration of the at least one alkali metal and/or the alkali metal oxide that increases from the surface in a direction of the interior in such a way that a maximum concentration of the at least one alkali metal and/or an alkali metal oxide is present at a distance of not more than 60 nanometres measured perpendicularly from the surface.

2. The element of claim 1, wherein the distance is not more than 20 nanometres.

3. The element of claim 1, wherein the concentration at the surface is at least 2% of the maximum concentration.

4. The element of claim 1, wherein the concentration at the surface is at least 10% of the maximum concentration.

5. The element of claim 1, wherein the concentration at the surface is not more than 90% of the maximum concentration.

6. The element of claim 1, further comprising a mean of the maximum concentration and the concentration at the surface that occurs at a distance of at least 1 nanometer and not more than 50 nanometres measured perpendicularly from the surface.

7. The element of claim 1, further comprising a mean of the maximum concentration and the concentration at the surface that occurs at a distance of at least 5 nanometers and not more than 25 nanometres measured perpendicularly from the surface.

8. The element of claim 1, wherein the glass comprises at least 0.5% by weight of sodium oxide and has a concentration of the sodium oxide that increases from a minimum value at or close to the surface in the direction of the interior, wherein the concentration of the sodium oxide has a plateau value in the interior beyond a distance of not more than 50 nanometres from the at least one surface that is constant, and wherein the concentration of the sodium oxide has a minimum value of at least 1% of the plateau value.

9. The element of claim 8, wherein the minimum value of the concentration of the sodium oxide is not more than 10% of the plateau value.

10. The element of claim 1, wherein the glass comprises at least 0.5% by weight of lithium oxide and has a concentration of the lithium oxide that increases from a minimum value at or close to the surface in the direction of the interior, and wherein the concentration of the lithium oxide has a plateau value in the interior beyond a distance of not more than 50 nanometers from the surface that is constant.

11. The element of claim 10, wherein the concentration of the lithium oxide has a minimum value that is at least 1.5% of the plateau value.

12. The element of claim 1, wherein the glass comprises at least 0.5% by weight of potassium oxide and has a concentration of the potassium oxide that increases from a minimum value at or close to the surface in the direction of the interior, and wherein the concentration of the potassium oxide has a plateau value in the interior beyond a distance of not more than 50 nanometres from the surface that is constant.

13. The element of claim 12, wherein the minimum value of the concentration of the potassium oxide is at least 1% of the plateau value.

14. The element of claim 1, wherein the glass comprises, measured at a distance of at least 50 nanometres measured perpendicularly from the surface, the following proportions in percent by weight on an oxide basis: silicon dioxide (SiO.sub.2) from 50 to 77 percent, aluminium oxide (Al.sub.2O.sub.3) from 0 to 10 percent, boron trioxide (B.sub.2O.sub.3) from 0 to 10 percent, iron(III) oxide (Fe.sub.2O.sub.3) from 0 to 10 percent, sodium oxide (Na.sub.2O) from 0 to 18 percent, potassium oxide (K.sub.2O) from 0 to 17 percent, lithium oxide (Li.sub.2O) from 0 to 6 percent, total oxides of Ca, Mg, Ba, Sr and/or Zn from 1 to 15 percent.

15. The element of claim 14, wherein the glass further comprises, measured at the distance of at least 50 nanometres measured perpendicularly from the surface, the following proportions in percent by weight on an oxide basis: fluorine (F) from 0 to 4 percent.

16. The element of claim 1, wherein the glass comprises Na.sub.2O and K.sub.2O, wherein the glass has a ratio of proportions in percent by weight of Na.sub.2O to K.sub.2O that is greater than 0.1.

17. The element of claim 16, wherein the ratio is greater than 1.4.

18. The element of claim 1, wherein the element is configured as a housing component for an electronic element, a housing for an element that is implantable in the human or animal body.

19. The element of claim 1, wherein the element is configured as a glass tube for reed switches or transponders or implants.

20. The element of claim 1, wherein the element is configured as a cylindrical glass tube with an exterior surface, an interior surface, and a uniform wall thickness therebetween.

21. The glass tube of claim 20, wherein the cylindrical glass tube has one or more of an external diameter of less than 6 millimetres, a ratio of the uniform wall thickness to the external diameter of less than , and a ratio of length to the external diameter of less than 50.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0088] FIGS. 1a and 1b are depth profiles of lithium ions generated by means of ToF-SIMS on four glass reed tubes;

[0089] FIGS. 2a and 2b are depth profiles of potassium ions generated by means of ToF-SIMS on four glass reed tubes;

[0090] FIGS. 3a and 3b are depth profiles of sodium ions generated by means of ToF-SIMS on four glass reed tubes;

[0091] FIGS. 4a and 4b are depth profiles of silicon ions generated by means of ToF-SIMS on four glass reed tubes;

[0092] FIGS. 5a and 5b are depth profiles of Na.sub.2O generated by means of ToF-SIMS on four glass reed tubes;

[0093] FIG. 6 is depth profiles of various glass components generated by means of ToF-SIMS on a glass reed tube;

[0094] FIG. 7 is a glass tube;

[0095] FIG. 8 is a transponder; and

[0096] FIG. 9 is a reed switch.

DETAILED DESCRIPTION

[0097] The measured depth profiles of various glass components shown in FIGS. 1a to 5b and FIG. 6 were determined on the exterior surfaces of four different glass reed tubes by means of time-of-flight secondary ion mass spectrometry (ToF-SIMS). The four glass tubes of FIG. 1a are of the same type here as the four glass tubes of FIG. 1b. The same applies to the glass tubes of FIGS. 2a and 2b, 3a and 3b, 4a and 4b, and also 5a and 5b.

[0098] In this ToF-SIMS method, a surface is bombarded with a high-energy primary ion beam, resulting in neutral particles, electrons and secondary ions being emitted from the surface. The secondary ions are separated as a function of their masses in a time-of-flight mass spectrometer (ToF spectrometer) and their relative number to one another is detected. This relative number is a measure of the concentration of the respective secondary ion as a function of the glass depth.

[0099] In FIGS. 1a and 1b, the concentration of lithium ions determined in this way is shown in the direction of the y axis. The concentration is plotted as a function of the depth in the direction of the x axis, that is to say as a function of the distance from the exterior surface of the glass element in the direction of the interior of the glass element. For this purpose, the rate of removal of material from the surface produced by the primary ion beam was determined and the depth in nanometres was thus calculated from the radiation time. The indications of x axis and y axis relate to a conventional two-dimensional Cartesian coordinate system in which the x axis runs horizontally and the y axis runs vertically, with the two axes intersecting at their respective zero value.

[0100] The four measured concentration profiles of lithium ions as a function of the depth 10, 12, 14 and 16 (FIG. 1a) were determined on four different glass reed tubes each having a diameter of 2.06 millimetres. The same applies to the profiles 10, 12, 14, 16 (FIG. 1b) on the same type of glass tubes in each case.

[0101] It should be noted that no absolute concentrations are determined by means of the ToF-SIMS method. To allow better comparability, the profiles were normalised to the intensity of silicon at the end of the measurement. The concentrations are accordingly plotted in arbitrary units (y axis). The concentration profiles 10, 12, 14 and 16 (and also 10, 12, 14 and 16) along in each case the y axis are thus relative values.

[0102] The measured concentration profiles of the lithium ions as a function of the depth 10, 12, 14 and 16 (and also 10, 12, 14 and 16) represent merely approximations of the concentration profiles actually present in the material because of the ToF-SIMS method. In particular, the fluctuations in the concentration profiles depicted are normal inaccuracies of such measurement methods.

[0103] In FIGS. 1a and 1b, the concentration determined in this way is shown as a function of the glass depth. Here, 10, 12, 14 and 16 (and also 10, 12, 14 and 16) were determined as a function of the depth on four different glass reed tubes each having a diameter of 2.06 millimetres.

[0104] The concentration profiles 10, 20, 30 and 40 are for the same sample. Likewise, the concentration profiles 12, 22, 32 and 42 can be assigned to one sample and the concentration profiles 14, 24, 34 and 44 to a further sample. An analogous situation also applies to the concentration profiles 16, 26, 36 and 46. A corresponding situation also applies to the concentration profiles 10, 20, 30 and 40, etc.

[0105] The lithium oxide concentration profile 10 measured on a first glass tube assumes a minimum value in the region close to the surface. The value increases in the direction of the interior of the glass tube. Beyond a distance of about 45 nanometres from the surface in the interior of the element, an essentially constant plateau value is attained. Here, the minimum value is about 2 percent of the plateau value.

[0106] The lithium oxide concentration profile 12 measured on a second glass tube displays a significantly different behaviour. A minimum value is attained at or close to the surface, and beyond a depth of only about 25 nanometres a plateau value, which represents the maximum value, is attained. Here, the minimum value is about 6 percent of the plateau value.

[0107] The lithium oxide concentration profile 14 measured on a third glass tube once again shows a behaviour similar to the profile 10. A minimum value is attained at or close to the surface. Beyond a depth of about 45 nanometres, a plateau value, which represents the maximum value, is attained. Here, the minimum value is about 2 percent of the plateau value.

[0108] A behaviour similar to the second glass tube is also observed for the concentration profile 16 of the fourth glass. Here too, the lithium ion concentration firstly decreases sharply at or close to the surface and then attains a plateau value at a depth of only about 25 nanometres. Here, the minimum value is about 3.5 percent of the plateau value.

[0109] The profiles shown in FIG. 1b correspond essentially to those of FIG. 1a.

[0110] In FIGS. 2a and 2b, the concentration of potassium determined in an analogous way is shown. Once again, four concentration profiles 20, 22, 24 and 26 (and also 20, 22, 24 and 26) were determined as a function of the depth on four different glass reed tubes each having a diameter of 2.06 millimetres.

[0111] The potassium concentration profile 20 measured on a first glass tube assumes a minimum value in the region close to the surface. The value increases in the direction of the interior of the glass tube. A maximum value is attained at a distance of about 10 nanometres. Beyond a distance of about 40 nanometres from the surface in the interior of the element, an essentially constant plateau value is attained. The minimum value of the concentration of the potassium is about 0.5 percent of the plateau value or of the maximum value.

[0112] The potassium concentration profile 22 measured on a second glass tube displays a somewhat different behaviour. A minimum value is attained at or close to the surface. A maximum value is attained at a depth of about 6 nanometres. Beyond a depth of about 25 nanometres, a plateau value is attained. The minimum value of the concentration of the potassium is about 6 percent of the plateau value or of the maximum value.

[0113] The potassium concentration profile 24 measured on a third glass tube displays behaviour similar to the profile 20. A minimum value is attained at or close to the surface. A maximum is attained at a depth of about 10 nanometres. Beyond a depth of about 40 nanometres, an essentially constant plateau value is attained. The minimum value of the concentration of the potassium is about 2 percent of the plateau value or of the maximum value.

[0114] A situation analogous to the profile 22 also applies to the concentration profile 26 of the fourth glass. Here, the maximum value is attained at a depth of about 6 nm. Beyond a depth of about 25 nm, a plateau value is attained. The minimum value of the concentration of the potassium is about 2 percent of the plateau value or of the maximum value.

[0115] The profiles shown in FIG. 2b correspond essentially to those of FIG. 2a.

[0116] FIGS. 3a and 3b show the concentration of sodium ions determined in an analogous way. Here, the sodium ion concentration is lowest in the region close to the surface for all samples. The concentration profiles 30 and 34 display a plateau value, which represents the maximum value, beyond depths of about 45 nm. In the case of the samples 32 and 36, the plateau value is attained at depths of about 30 nm. Here, the minimum value for the sample 30 is about 0.2% of the plateau value, in the case of the sample 32 is about 11% of the plateau value, in the case of the sample 34 is about 1.3% of the plateau value and in the case of the sample 36 is about 5% of the plateau value.

[0117] The profiles shown in FIG. 3b correspond essentially to those of FIG. 3a.

[0118] FIGS. 4a and 4b show the concentration of Na.sub.2O determined in an analogous way. Here, the sodium concentration firstly decreases in the region close to the surface for all samples. The concentration profiles 40, 44 display a plateau value, which represents the maximum value, beyond depths of about 40 nm. In the case of the samples 42, 46, the plateau value is attained at depths of about 25 nm.

[0119] The profiles shown in FIG. 4b correspond essentially to those of FIG. 4a.

[0120] In FIGS. 5a and 5b, the concentration profiles determined for the silicon ions are shown in an analogous way as a function of the glass depth. Here, all samples 50, 52, 54 and 56 have a maximum value in the regions close to the surface of the glass, and this subsequently decreases at about 30 to 40 nm so as to go over into a plateau value which at the same time represents the minimum value.

[0121] The profiles shown in FIG. 5b correspond essentially to those of FIG. 5a.

[0122] Overall, samples which correspond to the concentration profiles 12, 16, 22, 26, 32, 36, 42, 46, 52, 56 display more advantageous properties for achieving the object of the invention than the samples corresponding to the concentrations profiles 10, 14, 20, 24, 30, 34, 40, 44, 50, 54.

[0123] There is also the following relationship to the chemical resistance: glass elements having lower minimum values, in particular of sodium, potassium, lithium, at or close to the surface have an SiO.sub.2-rich surface. Such glass elements are therefore more chemically resistant, but can have a higher static charge.

[0124] However, the glass elements having relatively high minimum values at or close to the surface surprisingly also have good chemical resistance despite the reduced static charge.

[0125] FIG. 6 shows the concentration profiles of various ions determined in an analogous way of a sample. This sample, too, in the concentration profiles of the alkali metal ions sodium and lithium shows a reduction in the concentrations in the regions close to the surface with a subsequent concentration increase which goes over into a plateau. The concentration profile of the potassium ions firstly decreases in the regions close to the surface and subsequently assumes a maximum value at a depth of about 10 nm, which subsequently goes over into a plateau at about 20 nm.

[0126] In the case of the ions Si+, SiO+, B+and Al+, an increase in the concentrations in the regions close to the surface is firstly observed. With increasing depth, the concentration decreases and goes over into a plateau value which at the same time represents the minimum value.

[0127] FIG. 7 shows a glass tube 10 formed by a glass element comprising at least one alkali metal and/or an alkali metal oxide. The glass tube 10 has a length 16 and comprises a wall 14 with wall thickness 15. The glass tube 10 and/or the glass wall 14 have an exterior surface 11 as well as an interior surface 12, wherein the concentration of at least one alkali metal and/or the alkali metal oxide increases from one or both of the surfaces in the direction of the interior of the glass element specifically in such a way that the maximum concentration of this alkali metal and/or the alkali metal oxide in the glass element is present at a distance of not more than 60 nanometres measured perpendicularly from the surface or both surfaces.

[0128] FIG. 8 shows a reed switch 20 comprising a closed glass tube 10 forming the glass body of the reed switch 20. The reed switch 20 further comprises two leads 21 which extend through the wall of the glass tube 10. On the inside of the glass tube, the two leads 21 are forming or are connected to switch contacts 22. FIG. 9 shows a transponder 30 comprising a closed glass tube 10 forming the glass body of the transponder 30. In the internal volume of the closed glass tube 10, the transponder 30 further comprises a transponder element 31, such as an RFID element.