WO2015025043A1

WO2015025043A1 - Flat glass having a filtering effect

Info

Publication number: WO2015025043A1
Application number: PCT/EP2014/067929
Authority: WO
Inventors: Marta Krzyzak; Jens Ahrens; Bernd Kositz; Bianca Schreder; Lothar Niessner; Thomas Rossmeier; Carsten Lambert
Original assignee: Schott Ag
Priority date: 2013-08-22
Filing date: 2014-08-22
Publication date: 2015-02-26
Also published as: DE102013109087B3; TW201522270A

Abstract

The invention relates to a type of glass and a method for the production thereof. The glass according to the invention is characterized by a particularly steep UV edge and is suitable for many different applications, for example as a UV filter glass. The glass has excellent filtering properties which can be achieved by using certain UV filter components combined with a reduced melt.

Description

Flat glass with filter effect

This invention relates to a flat glass, to a process for its production and to uses of the flat glass and to a layer composite comprising the flat glass.

Flat glasses are used, for example, as cover glasses in picture frames or as coverslips in organic light-emitting diodes (OLEDs). Numerous flat glasses are already known from the prior art. An example is window glass.

However, conventional flat glasses have a serious disadvantage that makes them unsuitable for some applications: Conventional flat glasses allow a large proportion of UV radiation to pass through.

Depending on the intended application, the transmission of a glass to UV radiation is critical. If the flat glass is used, for example, as a cover glass in an OLED, the UV permeability is decisive for the life of the UV-sensitive emitter layer below the flat glass. The same applies, for example, to UV-sensitive paintings that hang in a picture frame with a flat glass as a cover glass.

There are numerous glass components that would generally be suitable for filtering out a UV component from light entering the glass. However, for many applications it has to be taken into account that the color of the light passing through the glass must not be changed.

In many applications, such as in OLEDs, technical applications, shop window glazing, restorative glass or glazing for pictures, a color-neutral appearance is desirable, especially for different viewing angles. It is also desirable that a - possible color neutral - glass simultaneously the function a protection of the picture colors or the natural or synthetic fibers and the dyes of the window displays against ultraviolet light takes over.

As is known, the UV component of sunlight or of lamp light, in particular in the case of metal halide or other gas discharge lamps, but also already in the case of halogen lamps, is sufficient to cause considerable damage over time such as discoloration or embrittlement of natural or synthetic materials.

Even for glazing in office or residential buildings, UV protection would be desirable to greatly reduce fading of wood surfaces, curtains, upholstered furniture, etc. in direct sunlight, thus allowing, for example, improved passive solar energy usage. Current heat-insulating glass containing a thin layer of silver does not visibly refract, nor does it provide sufficient UV protection because thin silver layers become transparent in the UV.

In the case of known antireflective soft glass, UV protection is achieved by using organic polymers as absorbers for UV light, for example as laminated glass, whereby two glass sheets are laminated together with a PVB plastic film, for example 380 μm thick, adapted to the glass in the refractive index. Such glasses are under intense lamplight, for example as an attachment for lamps, but not thermally stable and also degrade by intensive UV irradiation. Their one-sided Dreischichtentspiegelung also has the above limitations, the production of laminated glass is also consuming.

Another possibility is the use of UV-absorbing, but visible light-permeable lacquer layers with a few micrometers thick. Such paint layers are also not UV and temperature stable, and must be coated after application to the glass still. The following references teach flat glasses that are suitable for use as coverslips in OLEDs. None of the flat glasses has both the UV protection effect and the required colorlessness.

US 2010/0300535 A1 teaches a sodium-containing glass which can be used, for example, as substrate glass in photovoltaic applications. It is a flat glass. The glasses described have a low

Melting point for easier processing. The glasses described in this document do not have the excellent UV-filtering properties as those of the present invention. This is due, inter alia, to the fact that they were not melted reducing and moreover contain no cerium.

US 2006/0006786 A1 describes glass for gas discharge tubes, which are used in lamps. The glasses described therein are disclosed in very broad proportions. The content of alkali metal oxides and alkaline earth metal oxides is similar to that of the glasses of the present invention. However, the glass contains palladium, rhodium, platinum or iridium. These species are preferably not included in the glasses of the present invention. In addition, this document from the prior art did not recognize which advantageous effects can be achieved in the targeted selection of the components Co, Ti and Ce. It is used a lot of Ti0 ₂ and only a little Ce0 ₂ . In addition, the glass is not melted under reducing conditions.

US 2010/0047521 A1 describes a glass that can be used as protective glazing for electronic devices. The glasses should be transparent to IR radiation. The glasses described in this document do not have the excellent UV-filtering properties as those of the present invention, because they contain no cerium and are not melted reducing. In addition, they have very high levels of Al ₂ 0 ₃ , which greatly increases the crystallization tendency. US 2009/0325776 Al describes glass which has a certain ß-OH content. It can be used, for example, as a cover glass for electrical appliances. Although Ce0 _{2 is mentioned} as refining agent, but Ce0 _{2 works} only under oxidizing conditions as refining agent. Consequently, the glass described can not have the UV-filtering properties of the glasses of the present invention. In addition, the Al ₂ 0 ₃ content of the glasses presented in the document is very high.

EP 0 939 060 A1 describes a substrate glass for displays. The glasses discussed there are not filter glasses. In addition, quite high levels of Al ₂ 0 ₃ are used. Even because of the use of oxidatively acting refining agents (S0 ₃ , As ₂ 0 ₃ , Sb ₂ 0 ₃ ) and the absence of a UV filter component no UV filter glass can be obtained.

There is a need to produce glasses with filtering effect in an economical in-line production process for flat glasses. Such methods are for example Floaten, Draw Up, Down Draw and Overflow Fusion. In all these processes it is very important that the glass has a high resistance to crystallization and does not contain too high a proportion of reduction-sensitive components. This greatly complicates the formulation of corresponding glass compositions. Glasses that are processed by the methods mentioned must be kept at high temperature for a long time, which can easily lead to crystallization. Many conventional glasses are poured into blocks or other molds and rapidly cooled to prevent crystallization.

It is therefore an object of the invention to provide flat glass, which is suitable to protect UV-sensitive material from incident UV light and preferably barely or not at all to change the visible portion of passing through the glass light.

The object is solved by the subject matters of the claims. The flat glass of this invention contains Si0 ₂ in a proportion of at least 60% by weight and at most 76% by weight. Si0 ₂ is a network former. It provides the required chemical resistance and serves to adjust the viscosity properties. Flat glass should be as "long" glasses. This means that the viscosity as a function of temperature changes only slowly. This makes the glass melt can be more easily maintained in a required for shaping viscosity range is Si0 ₂ used in too small quantities. So the content of Si0 _{2 is} at least 64 wt .-%, more preferably at least 65.5 wt .-% and particularly preferably at least 66 wt .-% The content of this component is preferably limited to not more than 74 wt .-% and particularly preferably not more than 72 wt .-%.

The flat glass of this invention contains one or more alkali metal oxides in a proportion of at least 6% by weight and at most 25% by weight. Alkali metal oxides serve as a flux during the melt and lower the viscosity of the molten glass. So they are important for the production of flat glass, in particular, they facilitate the shaping. The alkali ions are very mobile due to their small size, so that on the one hand allows chemical hardening of the glass, but on the other hand, the chemical resistance of the glass is impaired. Therefore, the contents of alkali metal oxides should be chosen wisely. In preferred embodiments, the sheet glass of this invention contains alkali metal oxides in an amount of at least 8 wt%, more preferably at least 10 wt%, and most preferably at least 12.5 wt%. Their content should preferably not exceed a value of 21% by weight and more preferably 18% by weight, because otherwise the chemical resistance would be impaired too much. According to the invention, alkali metal oxides are preferably Li ₂ O, Na ₂ O and K ₂ O. In preferred embodiments, only Na ₂ O and / or K ₂ O are used. Lithium reduces the chemical resistance very much. The Na ₂ O content is preferably greater than the K ₂ O content. Na ₂ O is preferably used in a proportion of at least 5 wt .-% and at most 15 wt .-%. Particularly preferred is a range of 8 wt .-% to 12.5 wt .-%. K ₂ O is preferably used in a proportion of at least 1 wt .-% and at most 10 wt .-%. Particularly preferred is a range of 3.5 wt .-% to 7 wt .-%.

The flat glass of this invention further contains one or more alkaline earth metal oxides in an amount of at least 1% by weight and at most 21% by weight. Alkaline earth metal oxides are similar to the alkali metal oxides of adjusting the viscosity and lowering the melting temperature. However, the chemical resistance is not as severely impaired as when using alkali metal oxides. Preferably, the flat glass contains at least 4 wt .-% and at most 15 wt .-% alkaline earth metal oxides. According to the invention, the term "alkaline earth metal oxides" preferably denotes MgO, CaO, BaO and SrO, more preferably CaO, BaO and SrO and particularly preferably only CaO and BaO The proportion of alkaline earth metal oxides is preferably smaller than the proportion of alkali metal oxides in the glass according to the invention. Proportion is preferably greater than the BaO and / or ZnO content.

CaO is preferably contained in a proportion of at least 1% by weight and at most 10% by weight in the glass. It is preferably used in amounts of at least 2.5% by weight and at most 9% by weight, more preferably at least 3.5% by weight and at most 7% by weight. A preferred embodiment of the flat glass according to the invention contains BaO in a proportion of at most 6% by weight, preferably at most 4.5% by weight. Further preferred embodiments contain at least 1% by weight or at least 3% by weight.

Particularly good results with regard to viscosity of the melt,

Melting behavior and chemical resistance is achieved when the mass ratio of the sum of the alkali metal oxides to the sum of the alkaline earth metal oxides is less than 2 and preferably greater than 1.5. The plate glass of this invention may contain Al ₂ O ₃ in an amount of up to 6% by weight. Al ₂ 0 ₃ is a network former and thus serves for chemical resistance. It also increases the hardness of the flat glass. It also facilitates the chemical hardening of the flat glass when used in conjunction with alkali metal oxides. However, if it is used in too large amounts, this component increases the crystallization tendency of the glass, which makes production difficult. Overall, the melting behavior can be worsened. In preferred embodiments, the glass contains Al ₂ O ₃ in an amount of at least 0.5 wt% and at most 3.5 wt% or less than 3 wt%.

According to the invention, the sum of the components Si0 ₂ and Al ₂ O ₃ together is preferably at most 75% by weight, more preferably at most 74% by weight and particularly preferably at most 72% by weight, more preferably at most 70% by weight. If these components are used in excessive amounts, the melting behavior may deteriorate, which leads to increased costs during production.

Preferably, the present glass contains little or no B ₂ 0 ₃ . The content of B ₂ O ₃ is preferably below 5 wt .-%, more preferably below 2 wt .-% and particularly preferably below 0.5 wt .-%.

Preferably, the present glass contains little or no P ₂ 0 ₅ . The content of P ₂ O ₅ is preferably below 5 wt .-%, more preferably below 2 wt .-% and particularly preferably below 0.5 wt .-%.

The flat glass of this invention may contain ZnO in an amount of up to 4% by weight. ZnO has similar functions as the alkaline earth metal oxides, but it also reduces the crystallization tendency, so some embodiments are ZnO free. Other embodiments of this invention contain ZnO in proportions of at least 1 wt%, more preferably at least 1.5 wt%, and preferably at most 3.5 wt%. The sum of the components MgO, BaO, SrO and ZnO is preferably not more than 20% by weight, more preferably not more than 12% by weight, and particularly preferably not more than 10% by weight. However, this content is preferably at least 4 wt .-%, more preferably at least 5.5 wt .-%. These amounts have been found to be particularly advantageous for the adjustment of viscosity and melting properties.

The flat glasses of this invention contain cerium. This component is added to the mixture, preferably in the form of CeO ₂ ; but it can also be added already in the oxidation state Ce (III), for. B. in the form of CeCl ₃ , Ce (N0 ₃ ) ₃ or Ce ₂ 0 _3rd The content in the flat glass of this invention is expressed as CeO ₂ . When other cerium species are used, an amount corresponding to the amount (in moles) of these other cerium species is used. Ce ³⁺ and Ce ⁴⁺ serve to absorb UV radiation. The use of cerium as a UV absorber in flat glass is critical, because in the wrong oxidation state and / or too high concentrations cerium can cause a yellowish tinge. For this reason, the use of CeO ₂ in the flat glass of this invention is preferably limited to at most 8 wt%, more preferably at most 5 wt%, and most preferably at most 4 wt%. If the glass composition also contains TiO ₂ , the species Ce ³ -0-Ti ⁴⁺ may appear flattening the UV edge. When the term "cerium" is used in this specification, it means the element cerium in all its oxidation states, unlike prior art glasses, the glass of the present invention is prepared under reducing conditions, thereby increasing the content of Ce ^{3 +} with respect to Ce ⁴⁺ in glass. by means of this preparing, under reducing conditions, may have a very good absorption for UV radiation can be achieved with low cerium proportions.

CeO ₂ is preferably added in amounts of at least 0.1% by weight, more preferably at least 0.3% by weight, and more preferably at least 1% by weight, more preferably at least 2% by weight. The amount of cerium needed to achieve a particularly beneficial UV edge also depends on the thickness of the flat glass from. It has proven to be particularly advantageous to use the component cerium in an amount corresponding to a content of CeO ₂ of (2.5% by weight + d * 0, 1% by weight) ± 0.5% by weight. where d is the layer thickness of the flat glass in millimeters. With a layer thickness of 2 mm, the corresponding content of CeO _{2 should} therefore be more preferably 2.5% by weight + 2 * 0, 1% by weight = 2.7% by weight (± 0.5% by weight) ) amount.

In order for the UV edge of the flat glass of this invention to be as steep as possible, the flat glass is melted under reducing conditions. This ensures that a large part of the Ce0 ₂ derived Ce ^{4+ is} in the oxidation state Ce ³⁺ . Ce ⁴⁺ has its absorption maximum at about 280 nm, Ce ³⁺ at about 315 nm. It has proved to be helpful to adjust the ratio of Ce ³⁺ to Ce ⁴⁺ by reducing the melting conditions in favor of Ce ³⁺ , a particularly steep one To get UV edge. Unfortunately, the ratio of Ce ³⁺ to Ce ⁴⁺ in a finished glass according to the invention can not be measured quantitatively with sufficient reliability. However, the correct ratio of these two components can be well recognized on the transmission spectrum of the glasses, especially on the steep UV edge.

The reducing melting conditions are preferably achieved by adding a reducing agent to the mixture. The reducing agent is preferably used in amounts of up to 0.8% by weight, more preferably up to 0.5% by weight. It is the glass batch preferably before

Melt added. Preferred minimum amounts of reducing agent are 0.01 wt .-%, more preferably 0.1 wt .-% and particularly preferably 0.25 wt .-%. Preferred reducing agents are carbonaceous components and metals. Preferred carbonaceous components are carbon (eg in the form of coal, especially charcoal), sugar, starch and cellulose. Carbon is particularly preferred because it burns completely during the melt and thus is little or no detectable in the finished flat glass. Preferred metals are aluminum and silicon. By selecting the correct amount of CeO ₂ and the other glass components and with suitable reducing melt flow, a flat glass according to the invention with very good UV absorption is achieved with a steep UV edge.

The steepness of the UV edge is characterized in the flat glasses according to the invention in that the distance Δ of a first wavelength λ at which the flat glass has a transmission of 25%, of a second wavelength λ at which the flat glass has a transmission of 65%, at most 100 nm. Δ is preferably at most 50 nm, more preferably at most 25 nm, more preferably at most 15 nm, and particularly preferably at most 13 nm.

The layer thickness at which this transmission is measured is the thickness of the flat glass, which is preferably at least 0.1 mm, more preferably at least 1 mm, and particularly preferably at least 1.5 mm. The layer thickness is preferably at most 5 mm, more preferably at most 4 mm. In particularly preferred embodiments, the layer thickness is about 2 mm, 3 mm or 4 mm. In this case, in particular with regard to the wavelengths in nanometers, λ <λ Both wavelengths λ and λ are preferably in a wavelength range which lies in the region of the boundary between the UV and visible light, in particular in a wavelength range up to 400 nm, more preferably up to 390 Both wavelengths λ and λ are preferably in a wavelength range of at least 300 nm and more preferably at least 340 nm. λ is preferably in a wavelength range of 340 nm to 400 nm, more preferably 350 nm to 380 nm and particularly preferably 355 nm to 370 λ. λ is preferably in a wavelength range of 360 nm to 400 nm, more preferably from 365 nm to 395 nm and particularly preferably from 370 nm to 390 nm. The UV edge is located exactly between the wavelengths λ ₂₅ ° _{/ ο} and λ Thus, if λ is 360 nm and λ is 380 nm, then the UV edge mentioned in this description for the glass is at 370 nm. UV - Edge is preferably in a wavelength range of 300 nm to 400 nm, more preferably from 340 nm to 394 nm, more preferably from 350 nm to 390 nm and particularly preferably from 360 nm to 380 nm.

In order to mask any slight yellowing, CoO can be used in a proportion of up to 0.001% by weight. If too much CoO is used, the glass gets a blue color, which is not desirable. In a preferred embodiment, CoO is used in an amount of at least 0.0001% by weight. Since CoO is used to compensate for any slight yellowing caused by the cerium, the correct amount of CoO also depends on the amount of cerium. Preferably, the content of CoO is not more than one-thousandth of the content of cerium.

In order to avoid yellowing of the glass, it is preferred according to the invention that the content of cerium in relation to TiO _{2 is} particularly low. Preferably, the content of Ti0 _{2 is} at most 1/1000 of the content of cerium. Some preferred embodiments are Ti0 ₂ free.

The flat glass is in the range of visible light, i. E. from 400 nm to 780 nm, very transparent and neutral in color. The glass in this wavelength range preferably has continuous transmissions of at least 85% for layer thicknesses of 2 mm or even 4 mm. The plate glass of this invention preferably has a color rendering index (R _a ) of at least 99%, and more preferably even 100%, and is thus preferably color neutral. The color rendering index is determined according to DIN 6169 Part 2.

The permeability of the flat glass for UV radiation in the wavelength range from 280 to 350 nm is preferably not more than 20%, more preferably not more than 10%, more preferably not more than 5% and particularly preferably not more than 1% with layer thicknesses of 2 to 4 mm.

With a layer thickness of 2 mm over a wavelength range of 300 to 350 nm, the UV transmission is preferably not more than 10%, more preferably not more than 5%, more preferably not more than 1% and particularly preferably not more than 0.1 %. With a layer thickness of 2 mm over a wavelength range of 300 to 380 nm, the UV transmission is preferably not more than 20%, more preferably not more than 18% and particularly preferably not more than 16%.

The plate glass of this invention may contain ZrO ₂ in an amount of up to 2000 ppm due to the tub material used.

The flat glass of this invention is preferably free of TiO ₂ . Ti0 ₂ greatly affects the steepness of the UV edge, especially when used with cerium. The flat glass is furthermore preferably free of the harmful components PbO, As ₂ O ₃ and / or Sb ₂ O ₃ . Furthermore, preferably no further coloring components should be present, in particular the glass should be free of copper, manganese and / or chromium compounds. He ₂ 0 ₃ , NiO, Yb ₂ 0 ₃ , Bi ₂ 0 ₃ , Nd ₂ 0 ₃ , Pr ₂ 0 ₃ , Nb ₂ 0 ₃ , Ta ₂ 0 ₅ , Se0 ₂ , Mo0 ₃ and / or Ge0 ₂ are preferably also not contained in the glass. Preferably, the glass is also free of platinum, rhodium and iridium.

If it is said in this description that the glasses are free of a component or do not contain a certain component, it is meant that this component may at most be present as an impurity in the glasses. This means that it is not added in significant quantities. Non-essential amounts are inventively preferred amounts of less than 100 ppm, preferably less than 50 ppm and most preferably less than 10 ppm. The flat glass of this invention is preferably a thin glass having a thickness of at most 10 mm, more preferably at most 2 mm, more preferably 800 μm, preferably at most 600 μm, more preferably at most 400 μm and particularly preferably at most 300 μm. The flat glass of this invention has even with these low layer thicknesses still good filter properties for UV radiation. In addition, the flat glass at these layer thicknesses is still sufficiently flexible to be used, for example, in OLEDs.

The flat glass of this invention can be used as a filter glass. Use as a filter glass may be accomplished by placing the glass in front of a UV-sensitive article, such as an OLED, an electronic component (eg, CCD), or a painting. Further advantageous applications are uses as display glasses, in particular in tablet computers, mobile telephones, smartphones, monitors, televisions, notebooks, PDAs and navigation devices. The application in the field of outdoor lighting or in the automotive sector, for example as a glass to cover display instruments is according to the invention. According to the invention, in particular, a layer composite, such as an OLED, which contains at least one further layer in addition to the flat glass according to the invention as cover glass. According to the invention is also a product such as an OLED, a mobile phone, a computer, a tablet, a monitor, a television and the like, which contains a flat glass according to the invention as a cover glass.

According to the invention, the use of the glass as a heat protection glass, in showcases, showcases and office windows. The glass is particularly suitable for applications in which frequent cleaning of the glass is provided, especially when aggressive cleaning agents are used. Finally, no further coating is necessary for the filter effect, which could be impaired during cleaning. The glass is suitable for picture glazing in museums, but also for shop window glazing and restoration glasses. It is also suitable at the same time to take over the function of protection of picture colors or of natural or synthetic fibers and dyes of shop windows against ultraviolet light.

The flat glass of this invention may also be coated with functional coatings such as e.g. As antireflection, infrared-reflecting heat protective coatings, easy-to-clean coatings and / or ITO layers are coated. The reflection of the glass is less than 1%. Alternatively, the layers can be applied by sputtering (for example sputtering), by physical vapor deposition or by chemical vapor deposition, in particular plasma-assisted.

Thermal protection glasses are based on the principle of reflection of the infrared heat radiation through a thin, visibly predominantly transparent, electrically conductive coating. As the heat-reflective coating, tin oxide and silver-based layers are preferably used. Tin oxide can be applied immediately after glass production - and application of a diffusion-inhibiting SiOx pre-coating - in the cooling phase at about 600 ° C by means of a spraying process. By doping with fluorine or antimony, surface resistances are achieved at approx. 300 nm

Layer thickness up to 15 ohms, whereby averaged over the distribution of 300 K heat radiation averaged infrared reflectance of more than 80% is achieved. As window glazing, this glass thus reflects most of the heat radiation back into the space of a building.

Instead of doped tin oxide SnO ₂ : F, Sb, it is also possible to use the transparent semiconductor materials zinc oxide ZnO: Al (aluminum-doped) and indium oxide ln ₂ O ₃ : Sn (tin-doped, "ITO"). However, ITO has a much lower electrochemical stability than tin oxide and needed after the spraying process aftertreatments, zinc oxide can not be produced by means of spraying process with sufficient electrical conductivity.

Silver-based heat-reflecting coatings achieve significantly lower surface resistances down to 1 ohm, and thus infrared emissivities of 9 to 4%, in the limit of up to 2%, so that on the basis of such a coated disc in double-pane insulating glass k-values of 1 , 1 to 1.4 W / m ² K are possible. The visible transmission is a maximum of 76%, and decreases in the case of thicker silver layers for k-values below 1.0 W / m2K to about 68%. The UV transmission is 36-19%.

However, deposition of the silver layers, which are more favorable in terms of heat reflection, must be carried out quite expensively by means of a vacuum coating method after glass production, wherein further dielectric layers and possibly also metallic layers which surround the silver layer on both sides are also required for increasing transmission and long-term stability. Another disadvantage is that the silver-layer composite can always be applied only in the interior of double-pane insulating glass, since a permanent mechanical and chemical stability is not guaranteed compared to cleaning processes.

However, the UV transmission is still 25% with conventional heat protection glasses. By using a glass according to the invention, the UV transmission of heat protection glasses, when used, in particular when using about 4 mm thick glasses, can be reduced to <15%. The thicker the glass, the lower the UV transmission.

The glass can also be used for showcases or window glazing. The flat glass of this invention is obtainable by a method also according to the invention in which the components contained in the glass are mixed and melted together. During the melt reducing conditions are met, which can be achieved by adding a reducing agent to the mixture.

After the melt, the glass is preferably processed into a flat glass in an in-line production process. The corresponding method is preferably selected from down draw, draw up, float and overflow fusion or other suitable hot forming methods for thin glass such as rolls.

After fabrication, the glass may be laminated, coated, and / or thermally or chemically tempered in a post-processing step.

By pre-stressing the breaking strength is significantly increased. A preferred coating according to the invention is an antireflection and / or anti-fingerprint coating; these coatings further reduce the UV permeability.

Examples

A mixture of the following composition in wt.% Was prepared and melted into a glass:

The blends according to Table 1 were processed to a flat glass in a flat glass process.

Table 1

The glasses obtained had the compositions according to Table 2: Table 2

Table 3 shows some measurements taken on the glasses. Table 3

Description of the pictures

Figure 1 shows three transmission spectra of glasses according to the invention. It can be seen that all three glasses have transmission values of more than 90% over the entire visible range. The transmission is constant over the entire visible range, so that the color impression of the light passing through the glass is not changed. The three spectra shown belong to glasses with the same composition according to the invention. However, the samples were different in thickness. The thickness of the sample increases from left to right: the left spectrum concerns a sample with a thickness of 2 mm, the middle one with 3 mm and the right one a sample with a thickness of 4 mm. The UV edge therefore shifts slightly to the right in the direction of visible wavelengths as the sample thickness increases.

Figure 2 shows a transmission curve with a value for the steepness of the transmission curve Δ. The steepness of the UV edge is characterized in the flat glasses according to the invention in that the distance Δ of a first wavelength λ ₂ 5%, at which the flat glass has a transmission of 25%, of a second wavelength λ ₆₅ ο _{/ ο} , in which the Flat glass has a transmission of 65%, is very small. Figures 3 and 4 show that the UV edge of the glasses according to the invention is very steep. This applies in particular to the glasses B1 to B4. The UV edge of the glass B6 is at much smaller wavelengths than the other example glasses.

FIG. 5 shows the measured reflection characteristic of a glass Bl according to the invention with a thickness of 2 mm in the visible range from 380 to 780 nm coated with an antireflection coating. The residual reflection is below 1%, the UV transmission is below 16%.

Figure 6 shows the transmission spectrum of a glass according to the invention in the wavelength range 280 to 800 nm, prepared according to Embodiment 1 with an anti-reflection coating.

Claims

claims

1. Flat glass with the following components in weight percent

wherein the glass has a UV edge with a steepness which is characterized in that the distance Δ of a first wavelength λ at which the flat glass has a transmission of 25%, of a second wavelength λ at which the flat glass has a transmission of 65% has at most 100 nm.

2. Flat glass according to claim 1, having a content of Na ₂ 0 from 5 to 15 wt .-%.

3. Flat glass according to claim 1 or 2, having a content of K ₂ 0 from 1 to 10 wt .-%

4. Flat glass according to one of the preceding claims, with a content of CaO of 1 to 10 wt .-%.

5. Flat glass according to at least one of the preceding claims, wherein the glass is thermally or chemically biased.

6. Flat glass according to at least one of the preceding claims, with a content of Ce0 ₂ from 0, 1 to 5 wt .-%.

7. Flat glass according to at least one of the preceding claims, wherein the glass has been melted under reducing conditions, in particular by adding a reducing agent such as carbon in a proportion of up to 0.8 wt .-%.

8. Flat glass according to at least one of the preceding claims with a UV edge in a wavelength range of 300 to 400 nm.

9. A method for producing a filter glass according to any one of claims 1 to 8, comprising the steps: a. Providing a glass batch, b. Melting of the glass batch, c. Production of flat glass from the melt, wherein the glass batch, a reducing agent is added.

10. Use of a filter glass according to one of claims 1 to 8 as a UV filter glass.

11. Laminate comprising a filter glass according to one of claims 1 to 8 as a cover glass.