DE102005000664B4 - Method for adjusting the UV absorption of glasses and glass ceramics and use of glasses and glass ceramics - Google Patents

Abstract

A process for producing a transparent, UV-blocking glass or a glass-ceramic with a defined UV edge, wherein the glass composition
the following components in wt .-% comprises:
SiO ₂ 60-85% by weight
B ₂ O ₃ > 0-35% by weight
Al ₂ O ₃ 0-10% by weight
Li ₂ O 0-10% by weight
Na ₂ O 0-20% by weight
K ₂ O 0-20 wt .-%, wherein the
Li ₂ O + Na ₂ O + K ₂ O 0-25 wt .-% is and
MgO 0-8% by weight
CaO 0-20% by weight
SrO 0-5% by weight
BaO 0-5 wt .-%, wherein the
Σ MgO + CaO + SrO + BaO is 0-20% by weight and
TiO ₂ > 0.5-10% by weight,
characterized in that the glass
(a) is subjected to cooling immediately after melting with cooling rates of less than 500 K / min, the cooling rate being such that the glass has a shift in UV compared to a glass tube cooled at cooling rates> 500 K / min Edge of more than 5, especially more ...

Description

The The invention relates to a method for adjusting the UV absorption especially the UV edge of glasses and glass ceramics, as well as the use of a glass or a Glass ceramic with a defined UV edge in one Lamps.

Glasses to manufacture of gas discharge tubes, like fluorescent lamps are known per se. These glasses should especially strong UV-absorbing properties.

Fluorescent lights, in particular, miniaturized fluorescent lamps find particular in the manufacture of liquid crystal displays (LCD) and at the back illuminated displays (passive displays, so-called displays with a Backlighteinheit) as a light source use. For this application have such Fluorescence lights on very small dimensions and accordingly the glass has only a very small Thickness.

Glasses for such Applications have a permeability or transmission of visible light in particular to wavelength ranges of 400 nm, in particular 380 nm, which is relatively constant. In the UV range the transmission of the glass should be low, since gas discharge tubes, in particular Fluorescent lamps release a large amount of UV radiation during light generation, the for surrounding components, such as polymers and other plastics, a harmful Influence, so that they become brittle over time, which can lead to the unusability of the entire product. A particularly harmful emission line is that of mercury that is used to generate light at 313 nm. Glasses for applications in fluorescent lamps, this emission line should be as possible Completely absorb. Furthermore is one possible high absorption of the emission line at 364 nm desired.

From the US 5,747,399 A Fluorescent lamp glasses are known for the aforementioned use, which absorb UV radiation in the desired range. However, it has been found that such glasses in the visible wavelength range show a strong discoloration and optionally a strong solarization. Frequently, a yellowish brown discoloration already occurs during melting of the raw materials.

From the DE 198 42 942 A For example, a zirconia and lithium oxide borosilicate glass of high durability is known, which is particularly suitable for use as a fused glass with Fe-Co-Ni alloys. Such a glass may also contain coloring components such as Fe ₂ O ₃ , Cr ₂ O ₃ , CoO, as well as TiO ₂ .

The DE 10 2004 027 119 A1 describes a method for producing a visible ultraviolet absorbing ray absorbing glass wherein the sharpness and position of the ultraviolet absorbing edge is adjusted by the content of TiO ₂ .

From the DE 10 2004 027 120 A1 is a UV-absorbing glass with high resistance, especially for fluorescent lamps, as well as a method for production and its use known. The setting of the UV edge is carried out by appropriate addition of additives, such as TiO ₂ or Fe ₂ O ₃ .

In the US 4,565,791 A describes a glass for ophthalmological applications, which has specific refractive indices and Abbé numbers, as well as suitable densities. Such a glass shows a UV absorption edge between 310 and 335 nm and contains as UV absorber TiO ₂ . For the production of this glass is expressly described that in many cases a purification with chlorine is necessary because an As ₂ O ₃ and Sb ₂ O ₃ refining is not sufficient. Finally, it is also described herein that although such glasses are extremely thin, a combination of Fe ₂ O ₃ and TiO ₂ results in discoloration of the glass, therefore, only quartz raw materials with an iron content of less than 100 ppm should be used. In the examples, after the melting and the molding, starting from 480 ° C, a cooling method which is carried out at a cooling rate of 60 ° C / hour to room temperature will be described.

Borosilicate glasses with a low content of B ₂ O _{3 are also} known. Such zirconium oxide and lithium oxide borosilicate, for example, in the DE 19842942 A1 described. This glass has a high acid and Laugebeständigkeitung, as well as a resistance to hydrolysis and is particularly suitable for the fusion with Fe-Co-Ni alloys. Such a glass may also contain coloring components such as Fe ₂ O ₃ , Cr ₂ O ₃ , CoO, as well as TiO ₂ . However, it is known that the boron component in such glasses results in less chemical resistance. For this reason, so far glasses with a higher boron content, ie of more than 25 wt .-% not as glasses for use in gas Discharge tubes have been considered, since they have an extremely poor chemical resistance, so that it was previously assumed that under the prevailing aggressive conditions, the fluorescent layer containing such lamps reacts with the substrate glass.

A disadvantage of prior art fluorescent lamp glasses was that they exhibited only insufficient UV blocking. To achieve UV blocking, for example, TiO ₂ or Fe ₂ O _{3 was} added to these glasses. In particular, for effective UV blocking it has been found that the addition of TiO _{2 is} particularly suitable in order to achieve effective UV blocking with simultaneous high transmission in the visible wavelength range. Furthermore, TiO _{2 has} the advantage of having a particularly steep UV edge. A disadvantage of the addition of TiO ₂ to technical glasses, however, was that, especially in borosilicate glasses, segregation into different phases may occur, if this is not intentionally desired. This causes the glass to show a tyndall effect and become milky cloudy. This effect can occur at TiO ₂ contents of more than 2% by weight, in particular in borosilicate glasses. If the glass becomes cloudy due to a separation into different phases, such glasses can not be used in applications in which the transmission of the glass plays a decisive role. For example, such glasses are useless as lighting applications.

The object of the invention is thus to overcome the disadvantages of the prior art, in particular to provide a method which allows effective UV blocking at the lowest possible TiO ₂ content. In particular, the harmful mercury discharge line at 313 nm is to be blocked in the produced glass.

According to the invention Task solved by a method with which a glass is made, in which the glass components a Glass composition according to claim 1, which is directly after melting a slow cooling in particular cooling rates <500 K / min, preferably <200 K / min and 100 K / min, most preferably <50 and 10 K / min or after melting for a period of time heated to a temperature is, with the cooling rate or the time period chosen be compared that the glass has a shift of the UV edge to the cooled quickly from the melt to room temperature glass of at least 5 nm. in particular, a UV edge is sought, in the wavelength range between 300 nm and 350 nm, preferably 310 and 330 nm, especially preferably 313 nm and 325 nm and that the glass in the wavelength range is largely transparent above the UV edge.

Under The UV edge in nm is understood here as meaning the glass with a Thickness of 0.2 mm below the specified wavelength (to shorter wavelength towards) has a spectral transmittance of <0.1%.

The Inventors have now found that the location of the UV edge by a temperature treatment of a rapidly cooled and so surprisingly transparent in the visible wavelength range Influence glass.

Under Cool quickly is understood here that the glass is not subjected to any special cooling, that is directly exposed to the ambient room temperature.

In particular, the position of the UV edge can be influenced by targeted cooling or targeted temperature aftertreatment so that even for glasses with a low TiO ₂ content, blocking of the UV light for wavelengths <320 nm is achieved, ie the UV edge at more than 313 nm and thus the harmful mercury line is blocked at 313 nm.

Prefers is prepared according to the invention Glass in gas discharge tubes used.

The so produced glasses are surprisingly suitable as a substrate glass in gas discharge tubes, since the expected Reaction of glass and fluorescent layer at least under the Operation prevailing conditions does not take place and the glass sufficiently resistant to corrosion during operation.

Borosilicate glasses are particularly preferred as glasses for use in lamps. Borosilicate glasses comprise SiO ₂ as the first component, and B ₂ O ₃ , as further component alkali and / or alkaline earth metal oxide, such as. Li ₂ O, Na ₂ O, K ₂ O, CaO, MgO, SrO, BaO.

Borosilicate glasses with a content of B ₂ O ₃ between 5 and 10 wt .-% show a high chemical Resistance.

Borosilicate glasses with a content of B ₂ O ₃ between 10 and 25 wt .-% show good processability and a good adaptation of the thermal expansion (so-called CTE) to the metal tungsten and the alloy KOVAR.

Borosilicate glasses with a B ₂ O ₃ content in the range 25-35 wt .-% show when used as a lamp glass a low dielectric loss factor tan δ, which in particular when used in electrodeless gas discharge lamps, ie lamps whose electrodes are mounted outside the lamp envelope of Advantage is.

In general, the glasses described in this application comprise a TiO ₂ content in the range> 1-7% by weight, preferably> 1-5% by weight, very preferably> 1-4% by weight. Fe ₂ O ₃ is preferably contained in the glass in contents <500 ppm. Fe ₂ O ₃ is generally present as an impurity. However, Fe ₂ O ₃ can also be deliberately introduced for adjusting the UV edge, in which case the added contents are between 10-500 ppm, preferably 50-200, very preferably 70-150 ppm.

With particular preference, the sum of TiO ₂ + B ₂ O ₃ in the glasses produced here is in the range from 5 to 35% by weight, in particular in the range from 6 to 25% by weight.

In a first embodiment of the invention, the base glass produced usually contains at least 60% by weight SiO ₂ , with at least 61% by weight and preferably at least 63% by weight being preferred. A very particularly preferred minimum amount of SiO ₂ is 65% by weight. The maximum amount of SiO ₂ is 75% by weight, in particular 73% by weight, with 72% by weight and in particular not more than 70% by weight SiO _{2 being} very particularly preferred. B ₂ O ₃ is according to the invention in an amount more than 5 wt .-%, preferably more than 8 wt .-%, preferably more than 10 wt .-% and in particular at least 15 wt .-%, wherein at least 16 wt. % is particularly preferred. The maximum amount of B ₂ O ₃ is at most 35 wt .-%, but preferably at most 32 wt .-%, with a maximum of 30 wt .-% is particularly preferred.

Al ₂ O ₃ is contained in an amount of 0-10% by weight, with a minimum amount of 0.5% by weight or 1% by weight and especially 2% by weight being preferred. The maximum amount is usually 5 wt .-%, preferably 3 wt .-%. The individual alkali metal oxides Li ₂ O, Na ₂ O and K ₂ O are each independently 0-20, or 0-10 wt .-%, with a minimum amount of 0.1 wt .-%, or 0.2 and in particular 0.5 wt .-% is preferred. The maximum amount. individual alkali oxides is preferably at most 8 wt .-%, wherein an amount of Li ₂ O from 0.2 wt .-% to 1 wt .-%, for Na ₂ O 0.2 wt .-% to 1.5 wt. % and for K ₂ O 6-8 wt .-% is preferred. The sum of the alkali oxides in the basic glass according to the invention is 0-25% by weight and in particular 0.5-5% by weight. According to the invention, alkaline earth oxides, such as MgO, CaO, SrO, are contained in each case in an amount of 0-20% by weight and in particular in an amount of 0-8% by weight or 0-5% by weight. The sum of the alkaline earth oxides is according to the invention 0-20 wt .-%, preferably 0-10 wt .-%. In a particularly advantageous embodiment, they have together at least 0.5% by weight or> 1% by weight.

In addition, the produced base glass according to a first embodiment preferably contains 0-3 wt .-% ZnO, 0-3 and 0-5 wt .-% ZrO ₂ , 0-1 and 0-0.5 wt .-% CeO ₂ and 0-1 wt .-% and 0-0.5 wt .-% Fe ₂ O ₃ . In addition, it is also possible for WO ₃ , Bi ₂ O ₃ , MoO _{3 to be present} independently of one another in each case in an amount of 0-5% by weight or 0-3% by weight, but in particular of 0.1-3% by weight. be included.

It has been found that, although the glasses are very stable against solarization under UV irradiation, the solarization stability is due to low levels of PdO, PtO ₃ , PtO ₂ , PtO, RhO ₂ , RhO ₂ , Rh ₂ O ₃ , IrO ₂ and / or Ir ₂ O ₃ can be further increased. The usual maximum content of such substances is at most 0.1% by weight, preferably at most 0.01% by weight, with a maximum of 0.001% by weight being particularly preferred. The minimum content for these purposes is usually 0.01 ppm, with at least 0.05 ppm and especially at least 0.1 ppm being preferred.

Although the produced glasses may contain small amounts of CeO ₂ , PbO and Sb ₂ O ₃ for increasing chemical resistance, refining and processability, they are preferably free thereof.

If the TiO ₂ contents of the glass composition are> 2% by weight and a mixture with a total Fe ₂ O ₃ content of> 5 ppm is used, it is preferred to purify with As ₂ O ₃ and to melt with nitrate Zen. The addition of nitrate is preferably carried out as alkali nitrate with contents> 1 wt .-%, in order to suppress a coloration of the glass in the visible range.

Furthermore, it has also been found for the glasses that, in particular, a discoloration of the glasses in the visible wavelength range can be avoided, at least in part, by the glass melt being substantially free of chloride and, in particular, no chloride and / or Sb ₂ O ₃ for refining in the glass melt is added. Namely, it has been found according to the invention that a blue coloration of the glass, as occurs especially in the case of the use of TiO ₂ , can be avoided if chloride is omitted as refining agent. The maximum content of chloride and fluoride according to the invention is 2, in particular 1 wt .-%, wherein contents of max. 0.1 wt .-% are preferred.

Of Further, it has been shown that sulfates, such as. B. as refining be used, as well as the aforementioned means to one discoloration of the glass in the visible wavelength range to lead. It is therefore preferred to dispense with sulfates. The maximum salary of sulfate According to the invention 2, in particular 1 wt .-%, wherein contents of max. 0.1 wt .-% are preferred.

When visible wavelength range in the present application, the wavelength range between 320 nm and 780 nm understood.

In addition, it has been found for the glasses that the above-described disadvantages can be further avoided if a refining with As ₂ O ₃ , under oxidizing conditions is performed. Preferably, at least 80%, usually at least 90%, preferably at least 95% and in particular 99% of the TiO _{2 contained is present} as Ti ⁴⁺ . In many cases, even 99.9 and 99.99% of the titanium are present as Ti ⁴⁺ . In some cases, Ti ^{4 +} contents of 99.999% have been found to be useful. Oxidative conditions are therefore to be understood as meaning in particular those in which Ti ^{4+ is present} in the amount indicated above or is oxidized to this stage. These oxidative conditions can be easily achieved in the melt, for example, by adding nitrates, in particular alkali metal nitrates and / or alkaline earth metal nitrates. By injecting oxygen and / or dry air, an oxidative melt can be achieved. In addition, it is possible an oxidative melt by means of an oxidizing burner setting, z. B. when melting the batch to produce. By oxidative refining, for example, using nitrates with As ₂ O ₃ , in particular the formation of the ilmenite (FeTiO ₃ ) complex can be prevented. The appearance of this complex leads to a strong color in the visible range.

Although nitrate, preferably in the form of alkali and / or alkaline earth nitrates, is added to the glass during the melting, the NO ₃ concentration in the finished glass after refining is only a maximum of 0.01% by weight and in many cases 0.001 wt .-%.

The composition of the glasses produced according to the invention is in the range (in% by weight):
SiO ₂ 60-85% by weight
B ₂ O ₃ 0-35% by weight
Al ₂ O ₃ 0-10% by weight
Li ₂ O 0-10% by weight
Na ₂ O 0-20% by weight
K ₂ O 0-20 wt .-%, wherein the
Li ₂ O + Na ₂ O + K ₂ O 0-25 wt .-% is and
MgO 0-8% by weight
CaO 0-20% by weight
SrO 0-5% by weight
BaO 0-5 wt .-%, wherein the
Σ MgO + CaO + SrO + BaO is 0-20% by weight and
ZnO 0-8% by weight
ZrO ₂ 0-5 wt .-% as well
TiO ₂ > 0.5-10% by weight, preferably> 1-10% by weight
Fe ₂ O ₃ 0-5 wt .-% is.

Preferred glasses according to the invention produced in a first embodiment, for example, a composition of
SiO ₂ 60- <75% by weight
B ₂ O ₃ 5-35% by weight
Al ₂ O ₃ 0-10% by weight
Li ₂ O 0-10% by weight
Na ₂ O 0-20% by weight
K ₂ O 0-20 wt .-%, wherein the
Li ₂ O + Na ₂ O + K ₂ O 0-25 wt .-% is and
MgO 0-8% by weight
CaO 0-20% by weight
SrO 0-5% by weight
BaO 0-5 wt .-%, wherein the
Σ MgO + CaO + SrO + BaO is 0-20% by weight and
ZnO 0-3% by weight
ZrO ₂ 0-5 wt .-% as well
TiO ₂ > 0.5-10% by weight
Fe ₂ O ₃ 0-0.5% by weight
CeO ₂ 0-0.5% by weight
MnO ₂ 0-1% by weight
Nd ₂ O ₃ 0-1% by weight
WO ₃ 0-2% by weight
Bi ₂ O ₃ 0-5 wt.%
MoO ₃ 0-5 wt .-%,
As ₂ O ₃ 0-1% by weight
Sb ₂ O ₃ 0-1% by weight
SO ₄ ^2- 0-2% by weight
Cl ^- 0-2% by weight
F ^- 0-2 wt .-%, wherein the
Σ Fe ₂ O ₃ , CeO ₂ , TiO ₂ , PbO + As ₂ O ₃ + Sb ₂ O ₃ > 0.5-10% by weight, and wherein
Σ PdO + PtO ₃ + PtO ₂ + PtO + RhO ₂ + Rh ₂ O ₃ + IrO ₂ + Ir ₂ O ₃ 0.00001-0.1 wt%.

Another preferred composition contains
SiO ₂ 63-72% by weight
B ₂ O ₃ 15-22% by weight
Al ₂ O ₃ 0-3% by weight
Li ₂ O 0-5 wt.%
Na ₂ O 0-5 wt.%
K ₂ O 0-5 wt .-%, wherein the
Li ₂ O + Na ₂ O + K ₂ O is 0.5-5% by weight and
MgO 0-3% by weight
CaO 0-5 wt.%
SrO 0-3% by weight
BaO 0-3 wt .-%, wherein the
Σ MgO + CaO + SrO + BaO 0-5 wt .-% is and
ZnO 0-3% by weight
ZrO ₂ 0-5 wt .-%
TiO ₂ > 0.5-10% by weight
Fe ₂ O ₃ 0-0.5% by weight
CeO ₂ 0-0.5% by weight
MnO ₂ 0-1.0% by weight
Nd ₂ O ₃ 0-1.0% by weight
WO ₃ 0-2% by weight
Bi ₂ O ₃ 0-5 wt.%
MoO ₃ 0-5 wt.%
As ₂ O ₃ 0-1% by weight
Sb ₂ O ₃ 0-1% by weight
SO ₄ ( ^2- ) 0-2% by weight
Cl ^- 0-2% by weight
F ^- 0-2 wt .-% and where
ΣFe ₂ O ₃ , CeO ₂ , TiO ₂ , PbO + As ₂ O ₃ + Sb ₂ O ₃ 0.5-10% by weight.

All of the aforementioned glass compositions preferably contain the previously indicated amounts of Fe ₂ O ₃ and most preferably are substantially free of FeO.

In a second embodiment of the invention, the following glass composition is used, which is characterized by a particularly high chemical resistance to acids, alkalis and water:
SiO ₂ 60-85% by weight
B ₂ O ₃ 0-10% by weight
Al ₂ O ₃ 0-10% by weight
Li ₂ O 0-10% by weight
Na ₂ O 0-20% by weight
K ₂ O 0-20 wt .-%, wherein the
Li ₂ O + Na ₂ O + K ₂ O is 5-25 wt.% And
MgO 0-8% by weight
CaO 0-20% by weight
SrO 0-5% by weight
BaO 0-5 wt .-%, wherein the
Σ MgO + CaO + SrO + BaO is 3-20 wt.% And
ZnO 0-8% by weight
ZrO ₂ 0-5 wt .-% as well
TiO ₂ > 0.5-10% by weight
Fe ₂ O ₃ 0-5 wt.%
CeO ₂ 0-5 wt .-%
MnO ₂ 0-5% by weight
Nd ₂ O ₃ 0-1.0% by weight
WO ₃ 0-2% by weight
Bi ₂ O ₃ 0-5 wt.%
MoO ₃ 0-5 wt .-%,
PbO 0-5% by weight
As ₂ O ₃ 0-1% by weight
Sb ₂ O ₃ 0-1% by weight
the
ΣFe ₂ O ₃ + CeO ₂ + TiO ₂ + PbO + As ₂ O ₃ + Sb ₂ O ₃
is at least> 0.5-10% by weight,
the
Σ PdO + PtO ₃ + PtO ₂ + PtO + RhO ₂ + Rh ₂ O ₃ + IrO ₂ + Ir ₂ O ₃
0.1 wt .-% is, and
SO ₄ ^2- 0-2% by weight
Cl ^- 0-2% by weight
F ^- 0-2% by weight

The second embodiment of a glass suitable for the process has a minimum content of SiO ₂ of at least 60% by weight, preferably at least 62% by weight, with a minimum content of 64% by weight being particularly preferred. The maximum content of SiO ₂ in the glass according to the invention is at most 85 wt .-%, in particular 79 wt .-%, with a content of at most 75 wt .-% is preferred. A particularly preferred maximum level is 72% by weight.

The content of B ₂ O ₃ is at most 10 wt .-%, in particular at most 5 wt .-%, with a content of at most 4 wt .-% is preferred. Particularly preferred is a maximum content of B ₂ O ₃ of at most 3 wt .-%, with a content of at most 2 wt .-% is very particularly preferred. In individual cases, the glass according to the invention can also be completely free of B ₂ O ₃ . However, in a preferred embodiment it contains at least 0.1% by weight, with 0.5% by weight being preferred. Particularly preferred is a minimum content of 0.75 wt .-%, wherein 0.9 wt .-% is very particularly preferred.

Although the glass according to the second embodiment of the invention may be free of Al ₂ O ₃ in individual cases, it usually contains Al ₂ O ₃ in a minimum amount of 0.1, in particular 0.2 wt .-%. A minimum content of 0.3 is preferred, with minimum amounts of 0.7, in particular at least 1.0, being particularly preferred. The maximum amount of Al ₂ O ₃ is usually 10 wt .-%, with a maximum of 8 wt .-% are preferred. In many cases, a maximum amount of 5 wt .-%, in particular 4 wt .-% has been found to be sufficient.

The glasses according to the second embodiment contain alkali and alkaline earth oxides. The total content of alkali oxides is at least 5% by weight, in particular at least 6% by weight, preferably but at least 8 wt .-%, with a minimum total amount of alkali oxides of at least 10 wt .-% is particularly preferred. The maximum content of all alkali oxides is at most 25 wt .-%, with a maximum amount of 22 wt .-% and especially 20 wt .-% is particularly preferred. In many cases, a maximum of 18% by weight has proven sufficient. Of these, the content of Li ₂ O according to the invention is 0 wt .-% to at most 10 wt .-%, with a maximum amount of not more than 8 wt .-% and in particular at most 6 wt .-% is preferred. K ₂ O is obtained in an amount of at least 0 wt .-% and at most 20 wt .-%, with a minimum content of 0.01 wt .-%, preferably of 0.05 wt .-% is preferred. In some cases, a minimum content of 1.0% by weight has proved suitable. The maximum content of K ₂ O is in a preferred embodiment a maximum of 18 wt .-%, with a maximum of 15 and especially a maximum of 10 wt .-% are preferred. In many cases, a maximum content of 5 wt .-% has been found to be completely sufficient.

The individual content of Na ₂ O is in individual cases 0 wt .-% and at most 20 wt .-%. However, the content of Na ₂ O is preferably at least 3% by weight, in particular at least 5% by weight, with contents of at least 8% by weight, in particular at least 10% by weight, being preferred. In particularly preferred embodiments, sodium oxide is present in an amount of at least 12% by weight. Preferred maximum amounts of Na ₂ O are 18% by weight and 16% by weight, with an upper limit of 15% by weight being particularly preferred.

Of the Content of the individual alkaline earth oxides is for CaO a maximum of 20 wt .-%; in individual cases However, maximum contents of 18, in particular a maximum of 15 wt .-% are sufficient. Even though the glass according to the invention can also be free of calcium components, so contains the glass according to the invention but usually but at least 1% by weight of CaO, with contents of at least 2% by weight, especially at least 3 wt .-% are preferred. In practice has a minimum content of 4 wt .-% proved to be useful. The lower limit for MgO is in individual cases 0 wt .-%, but at least 1 wt .-% and preferably at least 2 wt .-% are preferred. The maximum salary of MgO in the glass according to the invention is 8 wt .-%, with a maximum of 7 and especially a maximum of 6 wt .-% preferred are. SrO and / or BaO can in the glass according to the invention completely accounts; however, it is preferably at least one or both of these two substances in an amount of 1 wt .-%, preferably contain at least 2 wt .-%. The total content of all obtained in the glass Alkaline earth oxides at least 3% by weight and at most 20 wt .-%, wherein a minimum content of 4 wt .-%, in particular 5 % By weight is preferred. In many cases, minimum levels have of 6 and 7 wt .-% proved to be useful. A preferred maximum limit of alkaline earth oxides 18 wt .-%, with a maximum of 15 wt .-% are preferred. In some cases has a maximum content of 12% by weight has proven sufficient.

The glass according to the second embodiment may be free of ZnO, but preferably contains a minimum amount of 0.1% by weight and a maximum content of at most 8% by weight, preferably at most 5% by weight, with maximum contents of 3% by weight. -% or 2 wt .-% may still be appropriate. ZrO ₂ is contained in an amount of 0-5 wt .-%, in particular 0-4 wt .-%, with a maximum level of 3 wt .-% has proven to be sufficient in many cases.

The glass according to the second embodiment is also distinguished in a preferred embodiment by a total content of TiO ₂ , PbO, As ₂ O ₃ and / or Sb ₂ O ₃ in an amount of at least 0.1% by weight and at most 2% by weight. %, in particular at most <1% by weight. The preferred minimum content of As ₂ O ₃ and / or Sb ₂ O _{3 is} at least 0.01% by weight, preferably at least 0.05% by weight and in particular at least 0.1% by weight. The usual maximum amount is at most 2 wt .-%, in particular at most 1.5 wt .-%, with a maximum of 1 wt .-% and in particular 0.8 wt .-% is particularly preferred. Among the above-mentioned elements, TiO _{2 is} preferably contained in the glass of the present invention, although it may in principle be free thereof, provided that the content of the other components mentioned above is correspondingly higher. The maximum content of TiO ₂ is preferably 8% by weight, with at most 5% by weight being preferred. A preferred minimum content of TiO ₂ is 1 wt .-%. The glass contains 0-5 wt .-% PbO, with a max. Content of 2% by weight, in particular max. 1 wt .-% is appropriate. Preferably, the glass is lead-free. The content of Fe ₂ O ₃ and / or CeO ₂ is in each case 0-5 wt .-%, with amounts of 0-1 and in particular 0-0.5 wt .-% are preferred. The content of MnO ₂ and / or Nd ₂ O ₃ is 0-5 wt .-%, with amounts of 0-2, in particular 0-1 wt .-% are preferred. The components Bi ₂ O ₃ and / or MoO ₃ are each contained in an amount of 0-5 wt .-%, preferably 0-4 wt .-% and As ₂ O ₃ and / or Sb ₂ O ₃ are each contained in the glass according to the invention in an amount of 0-1 wt .-%, wherein the subset of the minimum contents is preferably 0.1, in particular 0.2 wt .-%. The glass according to the invention optionally contains small amounts of SO ₄ ^2- from 0-2 wt .-%, and Cl ^- and / or F ^- also in an amount of 0-2 wt .-% in a preferred embodiment. The total amount to Fe ₂ O ₃ , CeO ₂ , TiO ₂ , PbO, As ₂ O ₃ and Sb ₂ O ₃ is 0.1-10 wt .-%, preferably> 1-8 wt .-%.

The produced glasses according to the first and the second embodiment are particularly suitable for the production of flat glass, in particular after the float process, wherein the production of tubular glass is particularly preferred. It is especially suitable for production of tubes with a diameter of at least 0.5 mm, especially at least 1 mm and a maximum of at most 2 cm, especially at most 1 cm. Particularly preferred tube diameter be between 2 mm and 5 mm. It has been shown that such roar a wall thickness of at least 0.05 mm, in particular at least 0.1 mm, wherein at least 0.2 mm are particularly preferred. Maximum wall thicknesses amount at the most 1 mm, where wall thicknesses of at most <0.8 mm and <0.7 mm, respectively are.

The produced according to the invention glasses, in particular borosilicate glasses, are particularly suitable for use in gas discharge tubes as well Fluorescent lamps, in particular miniaturized fluorescent lamps and are very special for lighting, especially for backlighting of electronic display devices, such as displays and LCD screens, such as mobile phones and computer monitors. Preferred displays as well as screens are so-called flat displays, in particular flat backlight arrangements. Particularly preferred are halogen-free Illuminants, such as those on the discharge of Xenon atoms are based (xenon lamps). This design has proven to be special proved environmentally friendly.

The glasses produced according to the invention preferably have low dielectric properties. The dielectric constant at 1 MHz at 25 ° C is a maximum of 12 and is preferably below 10, with values below 7 and especially below 5 being very particularly preferred. The dielectric loss factor tan δ [10 ^-4 ] is a maximum of 120 and preferably less than 100. Loss factors below 80 are particularly preferred, with values below 50 and below 30 being particularly suitable. Most preferred are values below 15.

The produced according to the invention glasses are especially suitable for using fluorescent lamps with external ones Electrodes as well for Fluorescent lamps in which the electrodes fused with the lamp glass are and pass through it, such as Kovar alloys, molybdenum and tungsten etc. suitable. With external electrodes these can be formed for example by an electrically conductive paste.

Farther preference is given to the use of the glasses produced here in the form from flat glass for flat glass discharge lamps.

According to the invention the glasses mentioned in particular according to the following embodiment first shaped into a semi-finished product.

The Production of the semi-finished products, for example by a hot forming process For example, can be done directly from the melt. For example A tube is made by removing the liquid glass from the melting tank on a so-called Danner whistle runs, from there to a pipe is pulled out. The tube may also have other methods, such as Example of the Velo-train or A-train are made. The expert these processes are known.

flat glass can over an up-draw or down-draw or via the float method. These processes are also known to the person skilled in the art.

hollow glass can be pressed or blown.

at the above-mentioned processes no defined cooling of the Glass.

For example that cools Glass at the pipe train after it has left the Danner pipe, for example within a very short time to room temperature. There is no or only an insignificant "cooling".

According to the invention can glasses subjected to a temperature treatment for adjusting the UV edge become. Due to the temperature treatment, both the UV edge, d. H. the UV blocking, as well as the transmission, in particular the Scattering of the glass, to be discontinued.

To set a specific UV edge, for example, a glass with the following composition is produced (in% by weight based on oxide): SiO ₂ 64.27 B ₂ O ₃ 19,03 Al ₂ O ₃ 2.65 Li ₂ O 0.65 Na ₂ O 0.72 K ₂ O 7.46 ZnO 0.60 TiO ₂ 4.5 As ₂ O ₃ 0.10

The Annealing at lower temperatures is particularly preferred when the UV edge exactly should be adjusted, since by the longer time a better process control guaranteed is.

The appropriate setting of the UV edge can also be done in a multi-step process be achieved, as is customary, for example, for the production of fluorescent lamps.

These Temperature aftertreatment can also be used in the further processing of Tube to be integrated. This is done, for example, during production so-called miniaturized gas discharge lamps or fluorescent lamps for backlights at least one more temperature treatment, during which the glass is completely or partially heated becomes. examples for Such processes are the alignment of the glass tube, the compensation of production-related ripples of the glass tube, the burn-in the fluorescent layer, the melting of the electrodes.

The Temperature post-treatment can be defined as a single treatment at a defined Temperature performed being at higher Temperature a shorter one Time is sufficient.

Also This tempering step can be done by going through a defined Temperature profiles are achieved, with different heating rates and holding times at certain temperatures are possible.

The Displacement of the UV edge does not have to be done by a downstream one Tempering step, but can also directly after melting the glass can be achieved by the glass in the desired hot forming process at a tempering temperature for is held for a certain time or subjected to a defined cooling is, preferably <500 K / min, more preferably <10 K / min particularly preferably <1 K / min z. B. 0.3 K / min (20 K / h).

The cooling process is always according to the invention performed directly after the melt.

in the Production process is the cooling rate preferably less than 1000 K / min, preferably less than 500 K / min more preferably less than 100 K / min and preferably less than 10 K / min, most preferably the cooling rate is less than 1 K / min.

Combinations of an annealing treatment directly after the melt in the hot forming process with a subsequent annealing process are also possible. In this case, a post-annealing at temperatures can take place, wherein T _H in the range T _H Tg ≦ T _H <Tg + 400 ° C and, where Tg the transformation temperature, for example, according to "Schott" Guide to Glass ", Heinz G. Pfaender, Chapman and Hall 1996, pp. 20-S. 22 ". The duration of the post-curing is suitably selected and is preferably in the range of a few seconds to 120 minutes.

The Invention will be described below with reference to the drawings and embodiments be described in more detail.

It demonstrate:

1 a so-called backlight with the invention shaded areas.

2 the basic form of a reflective base and substrate plate for a miniaturized backlight assembly.

3 a backlight arrangement with external electrodes,

4 a display arrangement with side-mounted fluorescent lights.

5 a diagram showing the shift of the UV edge by the annealing process according to the invention.

In 1 is the principal view of a low-pressure discharge lamp, in particular a fluorescent lamp, most preferably a miniaturized fluorescent lamp shown.

In 1 is a so-called backlight bulb made from a drawn tube. The middle part 10 is largely transparent and forms the lamp body. In the two open ends 12.1 . 12.2 are metal wires 14.1 . 14.2 the bushings inserted. These are merged, for example, annealing step with the transparent tube glass.

Preferably, the glass in the region of the bushings is selected so that the coefficient of expansion of the glass largely corresponds to the coefficient of expansion of the metal wires 14.1 . 14.2 matches.

In the 2 to 4 the use of such invention produced backlight lamps is shown by way of example.

In 2 is a special use is for those applications where single miniaturized fluorescent tubes 110 consisting of the glasses according to the invention are used parallel to each other and in a plate 130 with depressions 150 which reflect the emitted light on the display. Above the reflective plate 130 is a reflection layer 160 that is applied by the fluorescent tube 110 in the direction of the plate 130 radiated light as a kind of reflector evenly and thus ensures a homogeneous illumination of the display. This arrangement is preferably used for larger displays such. B. in televisions.

According to the embodiment in FIG 3 can the fluorescent tube 210 also outside on the display 202 be attached, in which case the light by means of serving as a light guide light transporting plate 250 , a so-called LGP (light guide plate), is decoupled evenly across the display. Such light-transporting plates have, for example, a rough surface over which light is coupled out. The fluorescent tubes may have external or internal electrodes.

Moreover, it is also possible to use them for such backlight arrangements in which the light-generating unit 310 directly in a structured disk 315 located. This is in 4 shown. The structuring is such that by means of parallel elevations, so-called barriers 380 with a predetermined width (W _rib ) in the disk, channels having a predetermined depth and a predetermined width (d _channel or W _channel ) are generated in which the discharge luminescent material 350 located. The channels form together with a phosphor layer 370 provided disk multiple radiation cavities 360.1 . 360.2 . 360.3 . 360.4 . 360.5 , In the 4 Backlight arrangement shown is an electrodeless gas discharge lamp, ie there are no feedthroughs, but only external electrodes 330a . 330b , In the 4 Shroud shown 410 may be a cloudy diffuser or a clear transparent glass depending on the system design. At the in 4 The electrodeless lamp system shown is called a so-called EEFL system (external electrode fluorescent lamp). In principle, however, an internal contact, ie an ignition of the plasma via internal electrodes possible. This kind of ignition is an alternative technology. Such systems are referred to as cold-cathode fluorescent lamp (CCFL) systems. The arrangements described above form a large, flat backlight and are therefore also referred to as Flachbacklight.

The Invention will be explained in more detail in the following examples.

It glasses according to the invention were prepared in known manner and with known glass compared from the prior art. This was the raw material melted in a silica glass crucible at about 1500 ° C.

In 5 is for a glass with the following composition: SiO ₂ 64.35 B ₂ O ₃ 19.0 Al ₂ O ₃ 2.65 Li ₂ O 0.65 Na ₂ O 0.70 K ₂ O 7.45 ZnO 0.60 As ₂ O ₃ 0.10 TiO ₂ 4.50 the shift of the UV edge is shown.

The glass tube would be made by the Danner method and cooled very rapidly, ie from about 1100 ° C to 300 ° C in less than a minute. The UV edge of this glass with a thickness d = 0.2 mm and a transmission T <0.1% was 302 nm. The curve is in 1 marked with 100. As can be clearly seen from the transmission spectrum, the slowly cooled sample, ie the sample cooled at 20 K / h, has a UV edge of 320 nm and includes the 313 nm line of the mercury lamp. The transmission curve of the slowly cooled sample is labeled 200. The TiO ₂ content was 4.5% by weight. The glass tube had a diameter of 3 mm, the thickness of the glass wall was 0.2 mm. The UV edge is characterized in this application by a transmittance T <0.1%.

alternative for slow cooling can also be a night annealing.

With the present invention, a method for shifting the UV edge of glasses and glass ceramics is specified for the first time, with which a UV absorption in the range greater than 313 nm is achieved even at low TiO ₂ contents. In this way, the turbidity, ie the Tyndall effect of the glass is reduced, since the TiO ₂ content is lower than for glasses which have a comparable edge layer with rapid cooling. According to the invention, the UV edge can be set by a defined cooling or heat treatment ie the setting of certain redox conditions by the cooling or heat treatment or shifted to higher wavelengths in comparison to rapidly cooled samples.

Claims (13)

A process for producing a transparent, UV-blocking glass or a glass ceramic with a defined UV edge, the glass composition comprising the following components in% by weight: SiO ₂ 60-85 wt.% B ₂ O ₃ > 0-35 wt % Al ₂ O ₃ 0-10% by weight Li ₂ O 0-10% by weight Na ₂ O 0-20% by weight K ₂ O 0-20% by weight, where the Σ Li ₂ O + Na ₂ O + K ₂ O 0-25 wt .-% and MgO 0-8 wt .-% CaO 0-20 wt .-% SrO 0-5 wt .-% BaO 0-5 wt .-% where the Σ MgO + CaO + SrO + BaO is 0-20% by weight and TiO ₂ > 0.5-10% by weight, characterized in that the glass (a) cools immediately after melting with cooling rates less than 500 K / min, the cooling rate being such that the glass, compared to a glass tube cooled at cooling rates> 500 K / min, has a UV edge shift greater than 5, in particular greater than 10 nm shows; or (b) after heating is subjected to a heating for a period of time to a temperature T _H , the time duration and the temperature being selected such that the glass is cooled in comparison to a glass tube cooled at cooling rates> 500 K / min. shows a shift of the UV edge of more than 5, in particular more than 10 nm. Method according to claim 1, characterized in that that led the process so is that the transmittance T <0.1 for wavelengths <340 nm. Method according to claim 2, characterized in that that led the process so is that the transmittance T <0.1 for wavelengths <320 nm. Method according to one of claims 1 to 3, characterized in that the temperature T _H in the range Tg <T _H <Tg + 400 ° C. Method according to one of claims 1 to 4, wherein the glass composition comprises the following components: SiO ₂ 60-75 wt .-% B ₂ O ₃ > 5-35 wt .-% Al ₂ O ₃ 0-10 wt .-% Li ₂ O 0-10% by weight Na ₂ O 0-20% by weight K ₂ O 0-20% by weight, where the Σ Li ₂ O + Na ₂ O + K ₂ O 0-25% by weight and MgO 0-8 wt .-% CaO 0-20 wt .-% SrO 0-5 wt .-% BaO 0-5 wt .-%, wherein the Σ MgO + CaO + SrO + BaO 0-20 wt. % ZnO and ZnO 0-3 wt .-% ZrO ₂ 0-5 wt .-% and TiO ₂ > 0.5-10 wt .-% Fe ₂ O ₃ 0-0.5 wt .-% CeO ₂ 0 -0.5 wt.% MnO ₂ 0-1.0 wt.% Nd ₂ O ₃ 0-1.0 wt.% WO ₃ 0-2 wt.% Bi ₂ O ₃ 0-5 wt. -% MoO ₃ 0-5 wt .-%, As ₂ O ₃ 0-1 wt .-% Sb ₂ O ₃ 0-1 wt .-% SO ₄ ^2- 0-2 wt .-% Cl ^- 0-2 Wt .-% F ^- 0-2 wt .-% wherein the Σ Fe ₂ O ₃ + CeO ₂ + TiO ₂ + PbO + As ₂ O ₃ + Sb ₂ O _{3 is} at least 0.5-10 wt .-%, and the glass has a content of PdO + PtO ₃ + PtO ₂ + PtO + RhO ₂ + Rh ₂ O ₃ + IrO ₂ + Ir ₂ O ₃ in a total amount of 0.00001-0.1 wt% eist. Method according to one of claims 1 to 5, wherein the glass composition comprises the following components: SiO ₂ 60-85 wt .-% B ₂ O ₃ 0-10 wt .-% Al ₂ O ₃ 0-10 wt .-% Li ₂ O. 0-10 wt% Na ₂ O 0-20 wt% K ₂ O 0-20 wt%, wherein the Σ Li ₂ 0 + Na ₂ O + K ₂ O is 5-25 wt% and MgO 0-8 wt.% CaO 0-20 wt.% SrO 0-5 wt.% BaO 0-5 wt.%, where the Σ MgO + CaO + SrO + BaO is 3-20 wt. % and ZnO 0-8 wt .-% ZrO 0-5 wt .-% and TiO ₂ <0.5-10 wt .-% Fe ₂ O ₃ 0-5 wt .-% CeO ₂ 0-5 wt.% MnO ₂ 0-5 wt.% Nd ₂ O ₃ 0-1.0 wt.% WO ₃ 0-2 wt.% Bi ₂ O ₃ 0-5 wt. % MoO ₃ 0-5 wt .-%, PbO 0-5 wt .-% As ₂ O ₃ 0-1 wt .-% Sb ₂ O ₃ 0-1 wt .-% wherein the Σ Fe ₂ O ₃ , CeO ₂ , TiO ₂ , PbO + As ₂ O ₃ + Sb ₂ O _{3 is} at least 0.5-10% by weight, where the ΣPdO + PtO ₃ + PtO ₂ + PtO + RhO ₂ + Rh ₂ O ₃ + IrO ₂ + Ir ₂ O wt .-% 0.1 is _3, and SO ₄ ^2- 0-2 wt .-% Cl ^- 0-2 wt .-% F ^- 0-2 wt .-%. Method according to one of claims 1 to 6, characterized in that the TiO ₂ content> 0.5-8 wt .-%, preferably> 1-6 wt .-%, more preferably> 2-5 wt .-% is , Use of a glass or a glass ceramic produced according to one of the claims 1 to 7 in a light source. Use according to claim 8, characterized in that the illuminant is a fluorescent lamp and the fluorescence is an EEFL lamp, a gas discharge lamp, a Lighting for LCD displays, computer monitors, telephone screens and displays is. Use according to claim 8 or 9, characterized in that the lighting means comprises a first and a second section and electrical feedthroughs and the feedthroughs are arranged in the region of the second section. Use according to one the claims 8 to 10, characterized in that the glass body of the luminous body a tubular or a tube-like Form has. Use according to claim 10, characterized in that the diameter of the tubular or tube-like Body is <0.8 cm and / or the wall thickness is <1 mm. Use according to one the claims 8 to 11, characterized in that the glass body of the filament a Flat glass with a thickness of <1 cm includes.