EP3713888A1 - Decorative coating having increased ir reflection - Google Patents

Abstract

The invention relates to a glass substrate or glass ceramic substrate comprising a surface region having a coating, which contains a glass matrix and IR-reflecting pigments, the IR-reflecting pigments having a TSR value determined in accordance with ASTM G 173 of at least 20% and the coating having a reflectance measured in accordance with ISO 13468 of at least 35% at a wavelength of 1500 nm. The invention further relates to a paste for producing an IR-reflecting layer, in particular on a glass substrate or glass ceramic substrate, comprising at least one IR-reflecting pigment and glass powder, and to a method for producing a corresponding coated substrate.

Description

Decorative coating with increased IR reflection

description

Field of the invention

In general, the invention relates to a coating with improved IR reflection as well as a paste and a

Process for the preparation of a correspondingly coated substrate. In particular, the invention relates to a

Decor coating with improved IR reflection, a correspondingly coated glass substrate and a

Household appliance with a correspondingly coated

Glass substrate.

State of the art

In domestic appliances such as ovens but also in chimneys occurs during operation naturally and desired

considerable heat development. However, at least for ovens, most of the heat should remain within the respective appliance as much as possible. Also

Fireplaces of chimneys should not be heated unnecessarily to avoid danger to the user

In the case of a baking oven, for example, a uniform temperature distribution within the oven should prevail during operation. For this purpose as well as for

Energy saving, it is necessary that the heat

if possible, remains in the device. In addition, it is also desired in terms of user safety that the respective Outer components, in particular the oven door, heat as little as possible. At the same time, however, the user should be able to observe the cooking or baking process during operation.

Therefore, oven doors usually have a structure of several, successively arranged glass layers on. To increase the thermal insulation effect, the individual glass panes are spaced apart

arranged so that the between the glass panes

air is the heat conduction by convection

diminished and thus acts as an insulating layer.

In addition to the heat conduction by convection, however, occurs in electric ovens or fireplaces heat conduction also due to the heat radiation generated during operation. Send here

For example, the heating elements of an electric furnace heat in the form of long-wave, electromagnetic radiation, the heat radiation approximately as

Blackbody radiation can be viewed. The

Wavelength of the radiation emitted by the heating elements is thus dependent on the respective temperature, so that the intensity maximum of the radiation depending on

Operating temperature in the range of 1.5 ym to 4.5 ym, in particular in the range of 2.5 ym to 10 ym may be.

In the prior art, various approaches to

Minimization of heat loss and to minimize heating of the door of a baking oven described.

Conventional ovens typically have doors with at least three spaced-apart panes of glass, the central pane being provided on both sides with a glass pane Coating which comprises a transparent, conductive oxide and is also referred to as low-E layer is coated. This coating is intended to cause a reflection of the long-wave IR radiation and thus a

Counteract heat loss by heat radiation.

 However, the disadvantage here is the relatively high cost of the conductive oxides.

Another disadvantage of the coating is that the oxides used for this purpose, such as

Indium tin oxide, fluorine-tin oxide, aluminum-zinc oxide and antimony-tin oxide do not show high scratch resistance or resistance. In addition, the reflection behavior of the corresponding oxides is often optimized for heat radiation in the area of solar heat radiation, since such layers were also borrowed from building glazings.

The outer disk, i. the disc that forms the outside of the oven door is usually additionally with a

Decorative layer provided. This decorative layer is usually applied as enamel or glass flow layer and preferably contains black, brown and / or white Pimente.

The decorative layer is applied mostly in the form of grid or dot matrix on the disc.

The patent application WO 2017/216483 A1 describes a coated flat glass with a multilayer coating comprising a layer with a transparent, conductive oxide and a black layer deposited thereon

Enamel layer as a decorative layer. This covers the

Enamel layer 10 to 60% of the flat glass surface. The particle size of those in the enamel layer Pigment particle is in the range of 500 nm to 10 ym and thus in the wavelength range of the heat radiation, so that the corresponding electromagnetic radiation to the

Pigment particles can be scattered. At the same time, however, the large particle size is disadvantageous in view of the processability of the pigments. Thus, corresponding enamel coatings are usually applied by screen printing on the substrate. With relatively large particle sizes, however, only screens with a correspondingly lower thread density can be used, which in turn can significantly limit the resolution of the printed decoration.

In this case, the pigment layer serves to enable an improved tempering process, essentially by virtue of the fact that far-infrared wavelengths which correspond to a temperature of more than 600 ° C, nor to

Heating the glass can be used and thus to an improved thermal curing of the glass including the double layer containing the conductive pigments

contribute.

Another way of reducing heat loss known in the art is to provide the furnace doors with reflective metal bands, such as silver or aluminum bands, thus directing the heat radiation back into the interior of the furnace.

Alternatively or additionally, the door design can also have forced convection cooling.

Corresponding structures, however, are complex in their construction and usually expensive. Object of the invention

It is therefore an object of the invention to provide a coated glass substrate which, in particular for electromagnetic radiation of a wavelength in the range of 1 to 4 μm, exhibits high reflection or remission and does not have or at least reduce the disadvantages described above. Furthermore, it is an object of the invention is a paste and a method for

Preparation of a corresponding coated substrate to provide. Another object of the invention is to provide an oven door or

Fireplace visor with improved heat insulation.

Brief description of the invention

The objects of the invention are already by the

Subject of the independent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

The invention relates to a paste for producing an IR-reflecting layer, in particular on a glass or glass-ceramic substrate, comprising at least one IR-reflecting pigment and glass powder. In this case, an IR-reflecting pigment is in particular a

Understood pigment having a remission of at least 50% at a wavelength of 1500 nm. Due to the high remission of the infrared (IR) radiation, a large part of the heat radiation is thus remitted or Remission was determined according to the standard ISO 134 68.

Furthermore, the pigment has a TSR of at least 20%. The TSR value (total solar reflectance) provides information on the percentage of reflected electromagnetic radiation in the wavelength range from 200 nm to 2500 nm and is determined in accordance with the ASTM G 173 measurement standards.

It has been shown here that a high TSR value of the pigments also improves the remission behavior of a coating produced from the paste compared to the

Thermal radiation influenced. In this case, a high TSR value is advantageous in order to achieve a high remission of the heat radiation, i. from electromagnetic radiation in the range of 1 to 4 ym. This is surprising insofar as the wavelength ranges of heat radiation and the

Wavelength range, which is relevant for the determination of the TSR value, only partially overlap. In particular, the TSR value as the transmission value for the solar radiation also refers to the wavelength range of 200 nm to 1000 nm, and thus to much lower

Wavelengths.

According to one embodiment, the paste at least one IR-reflecting pigment has a TSR value of at least 25%. Alternatively or additionally, the pigment at a wavelength of 1500 nm has a reflectance measured according to ISO 13468 of at least 60% or even at least 70%. One embodiment provides that the particles of the IR-reflecting pigment have a size distribution with a d50 value in the range from 0.5 μm to 2 μm. The small particle size makes it possible to apply the paste even with close-meshed screens, for example sieves with a thread count of 77 threads / cm or even 100 threads / cm, so that coatings or decors with high graphic resolution can be produced by screen printing , In the table below are

by way of example, but not limitation, some suitable sieves are listed.

In addition, the mesh size of the screen used together with the oil content and the powder densities determines the

Layer thickness of the coating after firing. According to a preferred embodiment, the IR-reflecting pigments have a particle size distribution with a d 50 value in the range from 0.8 μm to 1.8 μm.

Unlike the patent application WO 2017/216483 A1, the above-mentioned particle size is used.

Within the scope of the present disclosure, the

Pigment layer not to an improved

To enable biasing process and substantially lying in the far infrared wavelengths to heat the To use glass or the glass ceramic of the substrate, but it should be as well reflected or remitted to radiation in this way as little as possible heated glass or as little as possible heated

Glass ceramic of the respective coated substrate

provide. In the context of the present disclosure, in particular, in contrast, reflection and remission in a wavelength range which is at a temperature of approx.

150 ° C to a maximum of 500 ° C, to be as high as possible.

For the radiated power at different

Wavelengths are each assumed to be in the form of black body radiation, in which the emitted spectrum is defined by indication of the temperature. Thus, the presently disclosed

Temperatures corresponding spectra of

 Black body radiators are associated with high accuracy.

A further embodiment provides that the paste comprises a chromium-containing IR-reflecting pigment, preferably a chromium-containing iron oxide, a chromium-containing hematite and / or a chromium iron nickel spinel. The IR-reflecting pigment preferably has a black or black-brown color.

In particular, the respective pigments have a high thermal stability and a high chemical inertness to the glass components of the glass powder in the paste, in view of the penetration of the paste for producing the corresponding enamel coating

is particularly advantageous. Thus, according to a

Embodiment the possible maximum penetration temperature not limited by the stability of the pigments. This allows in a development of the invention the

Baking the paste on a glass or glass ceramic substrate at high temperatures in the range of 500 to 1000 ° C, so that during the Einbrandvorgangs the layer

Glass substrate can be thermally biased.

According to one embodiment of the invention, the glass powder contained in the paste has a

 Particle size distribution with a d50 value in the range of 0.1 ym and 3 ym and in particular in the range between 0.1 ym and 2 ym. Corresponding particle sizes ensure a homogeneous distribution of the pigments and the formation of a largely homogeneous glass layer during the

Einbrandvorgangs.

The glass in the paste preferably contains zinc oxide and / or bismuth oxide. Glass powder which has a content of zinc oxide in the range from 0.1 to 70% by weight and in particular one has proved to be particularly advantageous

Zinc oxide content in the range of 0.1 to 30 wt .-% have. Alternatively or additionally, the glass powder contains 0.1 to 75 wt .-% and in particular 8 to 75 wt .-% bismuth oxide. The content of zinc oxide or bismuth oxide in the above

described embodiments affects it

particularly advantageous to the softening temperature of the glass. According to a development of this

Embodiments include the glass powders

Softening temperatures in the range of 500 to 950 ° C.

Preferably, the softening temperature is less than 800 ° C, or even less than 750 ° C, and more preferably less than 680 ° C, but more than 450 ° C on. Due to the low softening temperatures already at low Einbrandtemperaturen the formation of a

homogeneous glass matrix or a glass flux from the

Glass powder. Thus, glass substrates with

different glass compositions (and thus

different softening temperatures) are coated with the paste, without the viscosity of the glass substrate to be coated is lowered during firing.

In addition, the content of bismuth oxide in the glass will correspond to the chemical resistance, i. the coating made with the paste increases.

Since the glass matrix or the glass flux in the coating of the coated substrate has the same composition as the glass powder in the paste, the

Details regarding the composition of the glass powder corresponding also to the composition of the glass matrix in the coating in some embodiments or

Further education.

According to one embodiment of the invention, the

Glass powder in the paste or the glass matrix of the

corresponding coating in wt .-% on the following coating:

Si0 ₂ 30-75 preferably 44-75

 Al 2 O 3 0-25 preferably 0.2-25, more preferably 2-25

 B2O3 0-30 preferably 1-30, particularly preferably 5-30

U ₂ 0 0-12

Na ₂ 0 0-25 prefers 0-15

 CaO 0-12

 MgO 0-9

BaO 0-27

The glass preferably has a minimum content of Al ₂ O ₃ of 0.2% by weight, preferably of at least 2% by weight.

Alternatively or additionally, the glass has a content of B ₂ O ₃ of at least 1% by weight, preferably at least 5% by weight.

It has also been found to be advantageous if the glass contains at least 1% by weight of an alkali metal oxide chosen from the group of Na ₂ O, Li ₂ O and K ₂ O or mixtures of these oxides.

Alternatively or additionally, the glass comprises at least 1% by weight of a further oxide or a mixture of oxides selected from the group of CaO, MgO, BaO, SrO, ZnO,

ZrÜ ₂ , and Ti0 ₂ .

According to another development, the glass has the following composition in% by weight:

Si0 ₂ 6-65, preferably 10-65, more preferably 15-65

In a preferred embodiment of the development, the glass has a minimum content of Si0 ₂ of 10 wt .-%, preferably of at least 15 wt .-%. Alternatively or additionally, the glass has a minimum content of Bi ₂ O ₃ of 5% by weight, preferably of at least 10% by weight.

Alternatively or additionally, the glass contains at least 1% by weight, preferably at least 3% by weight, of B ₂ O ₃ . Preferably, the total content of the alkali oxides Na _2Ü , Li ₂ 0 and K ₂ O is at least 1 wt .-%. The glass contained in the paste or the glass flux in the corresponding coating can in particular

alkali-free glass, an alkali containing glass, a silicate glass, a borosilicate glass, a zinc silicate glass

Zinc borate glass, a zinc borosilicate glass, a

Bismuth borosilicate glass, a bismuth borate glass, a

Bismuth silicate glass, a phosphate glass, a zinc phosphate glass, an aluminosilicate glass or a lithium aluminosilicate glass. According to one embodiment of the invention, the paste has glass powder with different

Glass compositions on.

According to one embodiment, the content of the

toxicologically questionable components lead, cadmium,

Mercury and / or chromium (VI I) _C onnectivity in the glass of less than 500 ppm.

Preferably, the content of conductive oxides in the

Paste, in particular of conductive oxides selected from the group consisting of the elements indium-tin oxide, fluorine-tin-oxide, aluminum-zinc-oxide and antimony-tin-oxide less than 500 ppm. In particular, none of the abovementioned oxides are added to the paste.

According to one embodiment of the invention, the paste comprises 10 to 40% by weight of IR-reflecting pigments, 45 to 85% by weight of glass powder and 12 to 35% by weight of screen printing medium. As solvents for screen-printable coating solutions, preference is given to using solvents having a vapor pressure of less than 10 bar, in particular less than 5 bar and very particularly less than 1 bar. These may be, for example, combinations of water, n-butanol, diethylene glycol monoethyl ether, Tripropylene glycol monomethyl ether, terpineol, n-butyl acetate. To be able to set the desired viscosity, corresponding organic and inorganic additives are used. Organic additives may include hydroxyethyl cellulose and / or hydroxypropyl cellulose and / or

Xanthan gum and / or polyvinyl alcohol and / or

Polyethylene alcohol and / or polyethylene glycol,

Block copolymers and / or triblock copolymers and / or tree resins and / or polyacrylates and / or polymethacrylates. As screen printing oils, for example, the oils listed in the table below can be used:

The composition of the paste described above ensures that a coating produced therefrom has a high IR reflectivity. At the same time, the proportion of the screen-printing medium ensures good processability of the paste, in particular processing by means of

Screen printing. Therefore, the paste preferably has a viscosity in the range of 3.5 Pa * s at a shear rate of 200 / s to 15 Pa * s at a shear rate of 200 / s, more preferably in the range of 4.8 Pa * s in one

Shear rate of 200 / s to 12.8 Pa * s at a shear rate of 200 / s.

According to one embodiment of the invention, the paste has a means which under temperature increase below

Formation of a volatile phase decomposes. By way of example, such agents are included which split off gas.

Preferably, the means are designed so that their

Anions in the temperature range of the viscous melt of the glass flux gas form and the cations of the agent without affecting the desired properties in the Glass matrix are involved. Such agents are also referred to as blowing agents or foaming agents.

Particularly suitable blowing agents are agents which contain carbides, carbonates or bicarbonates and

Manganese compounds include. Also, substances which are formed as hydroxides and / or water of crystallization

can be used as blowing agents.

For example, this includes salts, clay minerals, borates or aluminates. Phosphates or sulfates are also suitable as blowing agents. The mentioned exemplary

Blowing agents can be used alone or in mixtures.

In addition to the inorganic substances mentioned, organic substances can also be used as blowing agents.

For example, this includes substances which decompose at the temperatures considered here to form gas, in particular tartrates such as potassium bicarbonate, but also sugar or wood dust. Furthermore, advantageous results could be obtained with blowing agents comprising starch. In particular, it has been found that rice starch, corn starch and potato starch are particularly suitable as blowing agents.

Certain oxides decompose with elimination of a gas, such as cerium (IV) oxide or manganese (IV) oxide.

In general, a swelling or foaming agent is understood as meaning those agents which are found in

Increase temperature increase to form at least one volatile at Zerset _Z temperatur of the blowing agent volatile substance. As a volatile substance in this case in particular a gas understood. However, it should be noted that it is possible that at decomposition temperature

possibly developing volatile substance

Cooling of the coated substrate may be at room temperature in another state of aggregation. If, for example, decomposition temperature from a

Blowing agent forms water vapor as a volatile substance, it may be that after cooling of the coated substrate in the pore not more water vapor, but liquid water is present.

If the paste is exposed to high temperatures, pores are formed by decomposition of the blowing agent. A coating which has been applied to a substrate with a paste according to this development has closed pores. It is therefore assumed that the volatile substance which is volatile at Zerset _Z can be present at least partially in the pores of the coating. However, this does not necessarily have to be in a volatile form. For example, it is also possible that at

Zerset _Z non-volatile substance at room temperature is present as a condensate.

The spatial configuration or the shape of the pores can be influenced by the particular blowing agent used. In this case, it is possible to obtain porous enamels with pores having a largely symmetrical structure as well as porous enamels having anisotropically formed pores. Thus, in one embodiment of the invention, the paste contains calcium carbonate as a blowing agent. In this embodiment, the resulting pores when the paste is burnt in have symmetrical or at least substantially symmetrical structures, with the pores largely are spherical and a round or

have at least substantially round cross-section. The following table shows various blowing agents as well as the resulting pore forms.

In contrast, another embodiment provides for the use of rice starch as a blowing agent. The in this

Embodiment obtained porous enamel has pores with an anisotropic pore structure. In this case, the pores in particular have an ellipsoidal cross-section.

It has been found here that the IR reflection of the coating obtained by this development is higher than the IR reflection in embodiments with

unfoamed, i. non-porous enamels. This effect can be observed in particular in embodiments in which the coating predominantly has pores with a substantially spherical structure.

The inventors believe that the coatings include fully closed pores of the present invention Revelation some IR reflection in the form

have that a lowering of the temperature of one side, in particular the uncoated front of a window (the oven interior facing away from the oven inside, or the side facing away from the fireplace, the fireplace), for example, a oven door, or a window in a fireplace or a Furnace, in comparison to a coating which comprises no pores or only very few pores, in particular no or only very few closed pores, is present.

An exemplary list of suitable blowing agents, which are used alone or in combination as

Component of the paste can be found in the following table.

According to one embodiment of this development, the pastes for producing a porous, IR-reflecting coating contain a proportion of blowing agent in the range from 5 to 30% by volume, preferably from 5 to 15% by volume. Blähmittelanteile in this area have been found to be particularly advantageous in terms of the IR reflectivity of the resulting paste. It can be assumed here that structural elements are present through the interfaces of the pores in the coating, by means of which the IR reflectivity, for example by scattering effect, is increased. It can be assumed that these scattering effects occur especially in coatings with closed pores. However, high levels of blowing agents in the paste can cause open pores to form.

A development of the invention provides that the paste contains at least one further, second IR-reflecting pigment. Preference is given to the second IR-reflecting Pigment selected from the group of elements

Cobaltonitspineil, indium manganittrium oxide,

Niobium Sulfur Oxide, Tin Zinc Titanate,

 Cobalt titanate spinel. Preferably, the proportion of the second IR-reflecting pigment in the paste 0.5 to 15 wt .-%, preferably 3.5 to 12.5 wt .-%.

According to one embodiment, the volume ratio between the volume of the second pigment and the volume of the first pigment is 0.03 to 0.6, preferably 0.05 to 0.56 and particularly preferably 0.14 to 0.47.

Furthermore, the invention relates to a glass or

A glass-ceramic substrate comprising a surface area with a coating. Under a coating will

In particular, a surface region understood, which comprises a superficial diffusion of the coating in the near-surface regions of the substrate. The

Coating may thus also include diffusion layers at the boundary between the coating and the substrate. The coating contains a glass matrix and an IR-reflecting pigment, with the IR-reflective

Pigment has a TSR value of at least 20% measured according to the standard ASTM G173. In addition, the coating exhibits a reflectance of at least 35% measured at a wavelength of 1500 nm, in accordance with the measurement standard ISO 13468.

It has been shown here that a high TSR value of the pigments produces the remission behavior of the pigments

Coating also influenced against the heat radiation. Here, a high TSR value has been found to be advantageous for the remission of heat radiation of a temperature range of 200 to 475 ° C. This is insofar Surprisingly, since the corresponding wavelength for the abovementioned temperature range has its maximum in the range of 1 .mu.m to 4 .mu.m, the TSR value, on the other hand, refers to the solar spectrum with substantially smaller wavelengths in the range from 200 nm to 1000 nm. According to one

In a preferred embodiment, the pigment has a TSR of at least 25%.

The pigments are homogeneously distributed in the glass matrix, hereinafter also referred to as glass flow. According to one embodiment, the pigments have a

Particle size distribution with a d50 value in the range of 0.5 ym to 2 ym, preferably in the range of 0.8 ym to 1.8 ym. According to this embodiment, the pigments thus have a particle size which is below the wavelength of the heat radiation to be reflected.

 Surprisingly, the layer still shows a high remission for radiation in the IR range. Thus, the layers according to the invention have a remission of at least 35% at a wavelength of 1500 nm. According to a preferred embodiment, the remission at 1500 nm is at least 40% or even at least 45%.

According to one embodiment of the invention is the

Remission measured according to the standard ISO 134 68 for the entire wavelength range between 1500 nm and 2500 nm at least 35%, preferably at least 40% and particularly preferably at least 45%.

The proportion of the IR-reflecting pigment in the

Coating is 15 to 45 wt .-%, preferably 15 to 35 wt .-%. A corresponding pigment content ensures a sufficient IR remission of the coating. simultaneously the pigment content is small enough to be homogeneous

To allow distribution of the pigments in the glass matrix and to prevent or at least reduce aggregation of the pigment particles. The proportion of the glass matrix in the coating is preferably 55 to 85% by weight.

The extinction of electromagnetic radiation and the degree of its remission depends on the layer to be irradiated. The coating therefore preferably has a layer thickness in the range from 8 to 35 μm, preferably 10 to 20 μm. The coating is thus thick enough to allow a sufficiently high remission of the IR radiation

guarantee. The maximum layer thickness of 35 ym

at the same time ensures that mechanical stresses caused by different thermal

Coefficient of expansion (CTE) of coating and

Substrate occur, not the mechanical stability of the composite of substrate and coating adversely

and the coating can be used independently of the CTE of the substrate.

The use of chromium-containing pigments as IR-reflecting pigment has proven to be particularly advantageous. The coating preferably comprises, as the IR-reflecting pigment, a chromium-containing iron oxide, a chromium-containing hematite and / or a chromium iron comprising nickel spinel. These pigments have been found to be advantageous in terms of their spectral properties, in particular with regard to the remission in the IR range and with regard to their temperature stability.

 Here, the temperature stability of the pigments is not only for the use of the coated substrate,

For example, in a oven door or in a Kaminsichtscheibe, but also for the manufacturing process of the corresponding coating, which includes the penetration at temperatures in the range of 500 ° C to 1000 ° C, relevant.

The IR-reflecting pigment preferably has a black or black-brown color. In particular, the IR-reflecting pigment is selected from the group comprising the elements of the pigments Ci Brown 29, Ci Green 17 and Black CI 7.

In one development of the invention, the coating has at least a first and an IR-reflecting pigment. In particular, the color location of the coating can be adjusted by the second IR-reflecting pigment. The coating preferably contains, as the second IR-reflecting pigment, a cobalt chromite spinel, an indium manganittrium oxide, a niobium sulfur oxide, a tin zinc titanate and / or a cobalt titanate spinel. The use of one of the pigments from the group having the elements C. Pigment Blue 36, CI Pigment Blue 86, CI Pigment Yellow 227, CI Pigment Yellow 216, CI Pigment Green 26 and CI Pigment Green 50 has proven to be particularly advantageous.

The proportion of the second IR-reflecting pigment in the coating is preferably 0.75 to 18.5

Wt .-%, particularly preferably 4.5 and 14 wt .-%.

According to one embodiment, the volume ratio between the volume of the second pigment and the volume of the first pigment is 0.03 to 0.6, preferably 0.05 to 0.56 and particularly preferably 0.14 to 0.47. According to one embodiment of the invention, the content of conductive oxides in the coating is less than 500 ppm. In the context of the invention, conductive oxides are in particular transparent conductive oxides (TCO,

"Transparent conductive oxides") such as

Indium tin oxide, fluorine-tin oxide, aluminum-zinc oxide and antimony tin oxide understood.

One embodiment provides that the coating is applied directly to the substrate surface. Preferably, the glass or glass-ceramic substrate does not have a conductive oxide coating.

 In particular, no coatings comprising conductive oxides are arranged on the coating according to the invention and / or between the coating according to the invention and the glass or glass-ceramic substrate.

A development of the invention provides that the applied to the glass or glass ceramic substrate

Coating comprising closed pores. By using a coating in which the IR-reflecting pigments are present in a glass matrix or an enamel with closed pores, the IR reflection of the coating or the coated

Substrates be improved again. Therefore, the

Coating the present training so

configured to include closed pores. For this purpose, the suspension or paste comprises the present

Revelation in addition to the glass powder, an agent which increases in temperature to form a volatile

Substance decomposes. By way of example, the closed pores can be encompassed

Coating the present development, therefore, according to an embodiment also be designed as foam enamel. The coating is hereby used as a barrier to the passage of fluids, e.g. Water or too

Water vapor, formed. Accordingly, according to this embodiment, a glass or glass-ceramic substrate

provided, which in addition to a high IR reflectivity has a barrier effect against the entry and passage of fluids.

Fluids in the sense of the present disclosure preferably comprise liquids, in particular water, aqueous liquids, alcohols, on these liquids

based or comprising these fluids

Liquids, such as window cleaners, and / or oils and water vapor.

According to a further embodiment of this development, the coating is a high temperature stable,

self-sealing coating formed. A high-temperature-stable coating is understood in particular to mean a coating which is stable to temperatures of more than 400 ° C.

In the present case, a coating is referred to as self-sealing if no further coating is necessary in order to prevent sufficient sealing against the entry or passage of fluids. The layer thus has a barrier effect against fluids. The pores comprising coating according to this

Embodiments of the present invention is thus self-sealing, for example as a barrier to the passage of fluids formed.

Preferably, the porous coating is inorganic. However, the coating can also contain organic substances

include. These are generally not completely decomposed radical of organic compounds which have been added to the suspension or paste, for example in the form of solvents. These may also be the residues of incompletely decomposed, organically based blowing agents. According to one embodiment, the coating is substantially inorganic. Essentially inorganic here means that the

Coating comprises at least 95% by weight of inorganic constituents, preferably at least 98% by weight of inorganic compounds

Ingredients and particularly preferably at least 99 wt .-% of inorganic constituents. Most preferably, the proportion of the inorganic constituents of the coating is 99.9% by weight or more.

An embodiment provides that the resulting coefficient of thermal expansion of the porous coating and the coefficient of thermal expansion of the substrate differ from each other by not more than 4 * 10 ⁶ / K in the temperature range from 20 ° C to 700 ° C. Here, with regard to the coating on the resulting thermal

Expansibility coefficient turned off, since it is usually an inhomogeneous material in the coating, which materials with different

Expansion coefficient includes, in particular one

Glass flow and pores and optionally a pigment and / or other ingredients. So remarkable is not so far the resulting thermal expansion coefficient, which by the pore comprehensive structure and the coefficient of thermal expansion of the individual

Components of the coating results. According to one embodiment, the resulting thermal

Coefficient of expansion of the coating a value between at most 9 * 10 ^-6 / K and at least 3 * 10 ^-6 / K on.

According to a further embodiment of the invention, the substrate comprises a soda-lime glass or a borosilicate glass. Preferably, the glass is thermally toughened to increase strength.

A development of the invention provides that the

Coating has a refractive index n _{d, coating} in the range of 1.3 to 2, preferably in the range of 1.5 to 1.8

 A preferred embodiment of the invention provides that the coating is applied laterally structured on at least one surface of the glass or glass-ceramic substrate. This is under a lateral

Structuring in particular understood that only parts of the substrate surface are coated. In particular, at least 60%, preferably at least 62%, and most preferably at least 65%, are at least respective ones

Substrate surface coated with the coating. The high degree of occupancy of the substrate surface with the

Coating ensures a high IR reflection averaged over the entire substrate surface.

According to one embodiment of the invention is the

Coating laterally structured in the form of a grid or dot matrix on at least one of

Substrate surfaces applied. The grid or

grid-shaped pattern of the coating allows it Here, to achieve high occupancy levels while maintaining the transparency through the substrate.

The invention further relates to household appliances,

in particular ovens with an inventive

coated substrate.

One aspect of the invention in this case regards a baking-oven door with a pane construction with at least two panes, wherein the substrate coated according to the invention is used as an outer pane. In this case, the outer pane is understood to be the pane of the oven door which is in contact with the space surrounding the oven.

According to one embodiment of the invention, in this case, the substrate is a glass substrate and on one side with the

Coating provided. The coated side of the

Glass substrate in this case points in the direction of the furnace interior and at least 60%, preferably at least 62%, particularly preferably at least 65% and very particularly preferably at least 70% of the surface of the glass substrate are covered with the coating. Thus, the glass substrate preferably has an occupancy rate of at least 60%.

Already alone by the coating according to the invention, the heat loss can be significantly minimized by thermal radiation, so that depending on the application to further measures to reduce the heating of the outer

Disc can be dispensed with. Thus, according to one embodiment, the outer disc has no further

Coating comprising a conductive oxide. A development of the invention provides that the

Baking oven door comprises at least three glass panes and the outer and the middle glass pane are formed as inventively coated glass substrate. By using two slices coated according to the invention, the heat loss due to the escape of heat radiation as well as the heating of the oven door on the outside can be considerably reduced again. Preferably, the middle glass pane is provided on both sides with the coating according to the invention.

Substrates coated according to the invention can

For example, be used in chimney windows. Here have coated in particular

Glass ceramic substrates proved to be advantageous.

Furthermore, the invention relates to a method for

Production of a glass or glass-ceramic substrate comprising a surface area with a glass matrix and IR-reflecting pigments, in particular for producing a glass or glass-ceramic substrate according to one of claims 15 to 33, comprising at least the following steps: a) providing a glass or glass substrate

 Glass ceramic substrate, b) providing a paste comprising

Glass powder having a softening temperature T _EW , ci _aspuiver , at least one IR-reflecting pigment and a screen printing _medium , c) Lateral structured application of the in

 Step b) provided on the provided in step a) glass or

 Glass-ceramic substrate by means of screen printing, d) baking the applied in step c)

Layer at temperatures in the range of T _Einbranci

- TEW, glass powder

It has been found that further process step can be combined with the penetration in step d). Thus, a preferred variant of the method provides that in step a) a glass substrate, preferably a soda lime glass or a borosilicate glass is provided and the

Glass substrate in step d) is thermally biased together with the baking of the applied in step c) layer. This is made possible by the high

Temperature resistance of the pigments used.

Preferably, in step d), the burn-in and the thermal pre-stressing are carried out at a temperature in the range of 500 to 1000 ° C.

In a further preferred variant of the method, a crystallizable green glass is provided as substrate in step a). Here, in step d), a ceramization of the substrate take place simultaneously with the penetration of the layer. Both variants described above are advantageous in terms of energy and time savings.

In another variant that includes

Manufacturing process, with which a glass or

Glass-ceramic substrate, which can be coated

Preparation of a suspension or paste comprising a Blowing agents. According to this variant, the coating thus obtained is provided with pores in such a way that a coating, which is formed as a barrier to the passage of fluids, is present.

The method comprises the following steps: a. Preparation of a suspension or paste. The suspension comprises a glass powder and an agent which decomposes upon raising the temperature to form a volatile substance.

It has been found that particularly advantageous results can be achieved with blowing agents comprising carbonates and / or phosphates, in particular at layer thicknesses of the coating between 0.1 .mu.m and 500 .mu.m.

The glass powder is selected by way of example from the following composition range in% by weight:

The glass here advantageously comprises a minimum content of Al ₂ C> ₃ of 1 wt .-%, preferably of at least 2 wt .-%.

According to a further advantageous embodiment, the glass comprises at least 1 wt .-% B ₂ 0 ₃ , preferably at least 5 wt .-%. According to yet another advantageous

Embodiment, the glass comprises at least 1 wt .-% of an alkali metal oxide selected from the group of Na ₂ 0, Li ₂ 0 and K ₂ 0 or mixtures of these oxides.

According to yet another advantageous embodiment, the glass comprises at least 1% by weight of a further oxide or a mixture of oxides selected from the group of CaO, MgO, BaO, SrO, ZnO, ZrO ₂ , and TiO ₂ .

According to a further embodiment, the glass is selected from the following composition range in% by weight:

 The glass flux may further be selected from the following types of glasses: alkali-free glasses, alkaline glasses, silicate glasses, borosilicate glasses, zinc silicate glasses, zinc borate glasses, zinc borosilicate glasses,

 Bismuth borosilicate glasses, bismuth borate glasses,

 Bismuth silicate glasses, phosphate glasses, zinc phosphate glasses, aluminosilicate glasses or lithium aluminosilicate glasses.

Of course, it is also possible that the glass powder comprises mixtures of different glasses.

When preparing the suspension, it is possible to first introduce only the glass powder in a suspending agent. The suspending agent is formed as a liquid and may for example comprise water.

Preferably, the suspending agent comprises solvents, for example organic solvents. The solvents preferably have a vapor pressure of less than 10 bar, preferably less than 5 bar, and more preferably less than 1 bar. This includes, for example, water, 2- (2-butoxyethoxy) ethanol, 2-methoxy-methylethoxy-propanol, 2-butoxy-ethanol, n-butanol,

diethylene,

 Tripropylene glycol monomethyl ether, terpineol and n-butyl acetate, which are used alone or in mixtures

may be present. Also possible is the use of so-called commercially available screen printing oils.

In order to be able to set the desired viscosity, corresponding additives, which may be inorganic or organic, are used. Organic additives include, for example, hydroxyethyl cellulose and / or hydroxypropyl cellulose and / or xanthan and / or

Polyvinyl alcohol and / or polyethylene alcohol and / or

Polyethylene glycol, block copolymers and / or

 Triblock copolymers and / or tree resins and / or polyacrylates and / or polymethacrylates.

After the introduction of the powder into the suspending agent, the homogenization of the mixture takes place in a next step, for example in a three-roll chair.

It is also possible now to introduce another powder, which comprises, for example, the blowing agent, in a further suspending agent and to homogenize. Subsequently, the two suspensions can be mixed together.

It is also possible to first get a mix of

different powder, for example comprising a glass powder, a blowing agent and a pigment, and to homogenize this mixture, for example in a tumbler. Subsequently, this powder can then be pasted as described above.

The suspension preferably has a viscosity at a shear rate of 200 / s, measured with a cone plate viscometer, between 2,000 mPas and 20,000 mPas, preferably between 2,500 mPas and 15,000 mPas, particularly preferably between 3,000 mPas and 10,000 mPas. a. Apply the suspension to a substrate so that

 at least a part of the substrate are covered with the suspension.

The application of the suspension or paste to the substrate, such as a glass or glass ceramic substrate, in particular a glass or glass ceramic substrate with a low coefficient of thermal expansion, can take place over the entire surface, although it is also possible for the suspension to be applied in the form of specific patterns , For example, in this way patterns or

Font _Z oak or other raster are applied to the substrate.

In principle, all customary liquid coating methods are suitable as application methods. For example, the suspension can be applied in a printing process, in particular screen printing, pad printing or inkjet printing. Even a job in a decal process is possible. An application by means of spraying, spin coating or roll coating is also possible. For optimum processability of the

To ensure suspension, the suspension by various excipients, such as additives, Solvent or thixotropic agent on the

respective order procedures are adjusted. The

necessary, mostly organic, additives, volatilize when burned.

Particularly preferred application methods include ink-jet printing, offset printing, pad printing, wet decals,

Screen printing, dip coating, roller coating,

Spray coating, knife coating, flooding and spin coating. b. preferably fixing the suspension applied in step b to the substrate, preferably at a temperature between 0 ° C and 300 ° C.

After at least partial in step b

Application of the suspension to the substrate, such as a glass or glass ceramic substrate, is preferably carried out fixing the suspension on the substrate. This can be done for example by a drying step at elevated temperatures, for example at a temperature between 0 ° C and 300 ° C. The fixing of the suspension on the substrate is particularly advantageous if, after the successful application of the suspension to the substrate, it has to be transported to another process unit,

for example, to carry out further process steps.

Depending on the exact composition of the suspension have as preferred areas for fixing a

Temperature range between 0 ° C and 100 ° C and between 100 ° C and 300 ° C as preferred. During fixing, partial decomposition of the blowing agent may occur, which does not adversely affect further foaming at the firing temperature. In addition to the purely thermal fixation of the suspension on the substrate, it is also possible to support the fixing by IR radiation and / or by UV radiation. Also, with a suitable adjustment of the suspension, fixing can be effected solely by IR radiation and / or UV radiation. c. Annealing the at least partially coated

 Substrate at a temperature between 500 ° C and 900 ° C, so that the blowing agent decomposes to form at least one volatile substance and in the coating closed pores are formed.

Preferably, the annealing is carried out at a temperature between 500 ° C and 900 ° C.

During the annealing, on the one hand the decomposition of the blowing agent takes place, at the same time the penetration of the

Coating on the substrate. As a result, a closed-pore coating forms, which has a good adhesion to the substrate. d. Cool the substrate to room temperature.

According to an advantageous embodiment, the

Coating laterally structured in the form of a

predetermined pattern on the substrate, such as a glass or glass ceramic substrate applied.

It may also be advantageous if after the

Applying the suspension, a non-adherent support is applied to the layer and the support remains on the layer for the duration of the tempering. In this way, the layer remains uniformly thick. The appearance of disturbing uneven surfaces or corrugations is avoided. As "not liable" is a condition

especially when the edition after

After the heat treatment has taken place, it can be removed from the coating essentially without residue.

The application of the suspension is advantageously carried out by means of a printing process, for example by means of ink-jet printing, offset printing, pad printing or screen printing, or by means of rolling, flooding, dipping, spraying, knife coating or spin coating.

Detailed description of the invention

Hereinafter, the invention with reference to figures and

Embodiments described in more detail.

Show it:

Fig. 1 is a schematic representation of a

 according to the invention coated substrate as an embodiment,

Fig. 2 is a schematic representation of a coated

 Substrates as Comparative Example,

Fig. 3 is a graphical representation of total

 Transmission spectra (measured according to ASTM D 1003) of several embodiments and a comparative example,

4 shows the graphic representation of remission spectra

(measured according to ISO 13468) several Embodiments and one

 Comparative Example,

Fig. 5 is the graphical representation of

Color locus of the coating depends on the coating omposition _Z,

Fig. 6-8 are schematic representations for the construction of a

 Oven door according to one embodiment of the

 Invention and known from the prior art Comparative Examples,

9 is a schematic representation of the outer pane of a oven door with different degrees of occupancy,

10 and 11 are schematic representations of the structure

 different oven doors

12.13 shots of a thermal imaging camera of a baking oven with a glass pane coated according to the invention as an exemplary embodiment and of a baking oven with a conventionally coated pane as a comparative example,

Fig. 14 is a schematic representation of the measuring structure for

Determination of the surface temperature of the outer oven disk. By setting different temperatures, a pyrolysis operation at 468 ° C (875 ° F) or baking at 246 ° C (475 ° F) can be simulated. 15 is a schematic representation of the measuring structure for determining the surface temperature of the outer oven pane during the simulation of a baking process at 450 ° C,

16 is a graph of the

 Temperature variation of the temperature of the outer oven disc different

 Embodiment and the comparative example at an operating temperature of the oven of 475 ° F (246 ° C),

Fig. 17 is a graphic representation of the

 Temperature variation of the temperature of the outer oven disc different

 Embodiment and the comparative example at an operating temperature of the furnace of 875 ° F (468 ° C),

Fig. 18 is a graphical representation of

 Color locus shift of the coating depending on the glass composition in the coating,

Fig. 19 is a graphical representation of the in-line

 Transmissionsverlaufes different

 Embodiments (23 to 27) and the comparative example (22),

Fig. 20 is a diagram of a schematic

 Representation of a coated with a porous enamel substrate as a

Embodiment, wherein the porous enamel has largely isotropic pores, 21 is a graphical representation of a porous enamel coated substrate as another embodiment, wherein the porous enamel has largely anisotropic pores.

Fig. 22 is a graph of the measured

 Temperature variation of the maximum temperature of the outer oven disc different

 Embodiments which differ in terms of the porosity of the coating at an operating temperature of the furnace of 450 ° C and

FIG. 23 shows a representation of the averaged values of in

 Fig. 22 shown temperature curves and

Fig. 24 is a graph of the measured

 Curve of the maximum temperature of the outer oven disc at a

 Operating temperature of the oven of 450 ° C, where the decors with different layer thicknesses before

 Branding was applied.

Fig. 1 shows the schematic representation of a

Embodiment of a coating according to the invention

Substrates in side view. In the illustrated

Embodiment, the coating 2 is applied to one of the surfaces of the substrate 1, while the other surface 110 of the substrate 1 is uncoated. The coating 2 is in this case laterally structured on the surface region of the substrate 1 shown in FIG. 1, so that substrate 1 also has uncoated regions 120 on the coated surface 100. The Coating 2 can be applied, for example, in the form of a grid or in the form of a dot matrix. The degree of coverage of the substrate is understood to mean the ratio of the coated surface to the entire surface 100.

Fig. 2 shows the schematic representation of a

 Comparative example. Here, the substrate 1 is provided over its entire surface with a coating 3, which contains conductive oxides, such as indium tin oxide. The coating 3 thus represents the IR-reflecting layer in the comparative example. A pigmented decorative layer 4 is also applied to the layer 3. in the

 In contrast to the exemplary embodiment shown in FIG. 1, layer 4 is merely a decorative layer.

In the following, the production of the coated shown in Fig. 1 is based on an embodiment

 Substrates will be explained in more detail.

For the production of the coated shown in Fig. 1

 Substrate is first a paste comprising an IR-reflecting pigment, a glass powder and a

 Anpastmedium provided. Table 1 lists various IR-reflecting pigments which are known as

 particularly advantageous. For pigment no.

5 is a comparative pigment.

Table 1: IR-reflecting pigments and

 Comparative Example 5 To produce the glass powder or the glass frit, the individual glass components are mixed, melted and the molten glass quenched, and a glass powder having the desired particle size and particle size distribution is obtained by grinding processes. The glass powder

 (Coating glass component) can have very different compositions. There are many

 Glass compositions are known which, adapted to the deformation temperature of the substrate to be coated, a softening range of about 500 ° C to 1000 ° C.

 cover.

Table 2 shows some glass compositions or

 Glass powder that proves to be particularly beneficial

have exposed.

The glass powders listed in Table 2 have proven to be particularly advantageous in terms of

Processability during the manufacturing process of the coated substrate as well as in view of the optical, mechanical and chemical properties of the corresponding coating exposed.

To ensure a good processability is

For example, the softening temperature (T _E w, ci _{aspuiver) of} the glass relevant because for the smooth flow, ie for

Preparation of the coating from the applied paste, the penetration temperature must be at least the

Softening temperature Ew of the glass powder correspond. The softening temperature Ew is the temperature at which the viscosity of the glass is 10 ⁷ _' ⁶ dPas. Depending on the disc geometry and the heating process will be

Deformations, for example, in substrates of glass already observed significantly below their Ew. The smooth flow of the glass component into a layer is required to ensure the required chemical, physical, mechanical and optical properties. Also for the fixation of the added pigments and other fillers or additives, the smooth flow is necessary.

Furthermore, properties such as the chemical

Resistance to acids and bases or

hydrolytic attacks as well as the cleanability and scratch resistance important selection criteria. At the in

Table 2 listed glasses meet these requirements in a particularly advantageous manner. From the pigments and glass powders shown in Tables 1 and 2, the coatings 1 to 8 in Table 3 were obtained. Example 9 is a

Comparative Example.

Table 3: Embodiments 1 to 8 and

Comparative Example 9

In Fig. 3, the transmission curve of

Exemplary embodiments 1 to 4 and one

Comparative example shown. The transmission is the total transmission measured according to the ASTM D1003 standard. The curve 60 corresponds to the embodiment 1, the curve 61 of the embodiment 2, curve 62 of the embodiment 3 and curve 63 of the embodiment 4. The

Coatings were screen printed in one

Printing process applied with a sieve of a mesh size of 77 threads / cm and have a layer thickness in the

Range from 11 to 15 ym.

Curve 5 represents the transmission of Comparative Sample 9 and was applied with a 43 mesh / cm mesh screen. Here lies the layer thickness over the

Layer thicknesses of the embodiments.

It becomes clear that the transmission of the

Embodiments especially in the longer wavelength range of 1500 nm below the transmission of the comparative example. It should be noted that the

Layer thickness of Vergleichsprobegrößer is as the

Layer thickness of the embodiments. It can therefore be assumed that the distinction in the

Transmission values between execution and

Comparative example will be even more pronounced for layers of the same layer thicknesses. In addition, it is clear from the curves 60 to 63 that the IR-reflecting pigment used has a greater influence on the transmission as the glass composition of the glass matrix. Thus, the layers of the transmission curves 60 and 61 differ in their glass composition, but have the same pigment. The same applies to the layers of the curves 62 and 63. The samples 60 and 62, however, have the same glass composition, but differ by the pigment used.

FIG. 4 shows the wavelength characteristic of the remission of samples 7 and 8 as well as comparative example 9 from table 3. The remission process shown in FIG. 4 is the total remission measured according to measurement standard ISO 13468. Samples 7 and 8 differ in this case in their glass composition, but have the same IR-reflecting pigment. The curves 71 and 73 are assigned to the embodiment 7 of Table 3, wherein the individual layers differ with respect to the layer thickness. Curve 71 corresponds to the remission curve of the embodiment 7, wherein the coating by 2 printing operations with a sieve of

Mesh thickness was applied with 77 threads / cm and the layer has a layer thickness of 24 to 28 ym, the layer of the curve 73 was replaced by a simple

Applied printing and has a layer thickness of 11 to 15 ym. The same applies to the

Correspondence of the curves 72 and 74, the

Example 8 are assigned from Table 3. The layer thickness of the layer with the curve through 72nd

In this case, the course of remission shown here is 24 to 28 μm and the layer thickness of the layer with the remission curve represented by curve 74 is 11 to 15 μm. At these layer thicknesses, the stresses also relax larger deviations of the thermal expansion, without causing flaking or strength problems.

From Fig. 4 it is clear that the remission of

layers according to the invention in the IR range, in particular in the relevant for the remission of heat radiation at temperatures in the range of 200 to 475 ° C range of more than 1500 nm significantly above the remission of

Comparative example is. In addition, it becomes clear that the glass composition also has an influence on the remission in the IR range, whereby this influence increases with increasing

Layer thickness of the coating increases.

Fig. 5 shows the influence of various pigments in the coating on the color location of the coating, determined with a D65 light source measured from the color side in accordance with the measurement standard EN ISO 11664-4. Here, the reference numeral 80 shows the color location of a coating according to the

Embodiment 8 from the table. The coating was made by a simple printing process with a screen of mesh size of 77 threads / cm with nominal

Yarn diameter 55 ym applied to the substrate and has a layer thickness of 11 to 15 ym. The color location of the sample 80 is shifted here into the yellow color space. In contrast, the samples 81 and 82 have a slight yellow shift, in particular sample 81 shows a strong shift in relation to sample 80

Neutral range. This color locus shift is caused by the addition of a second IR-reflecting pigment. Table 4 shows the pigment composition of Coatings 80 to 82.

Table 4: Pigment compositions of FIG. 5

 6 shows a schematic representation of the arrangement of the glass panes in one of the prior art

known oven door. The oven door has in this case three thermally toughened glass sheets 8, 9 and 10 with the glass sheet 8 as the outer pane and 10 as the inner

Glass pane. Thus, disc 10 points into the interior of the oven and disc 8 limits the oven door to the outside.

The disks 8 and 9 additionally have coatings 3, 4 on one or two of the surfaces of the glass substrate 1. The outer disk 8 has in this case on the

 Interior of the furnace side facing a two-ply

Coating comprising a coating 3 with a transparent, conductive oxide and one on top

deposited decorative layer 4 on. The decorative layer 4 is an enamel layer containing a black or brown pigment in a glass matrix. The layer 4 acts here as a pure decorative layer, a backscatter from the

Furnace interior exiting heat radiation takes place only or almost only through the oxide layer 3. To increase the

Backscattering of the thermal radiation into the interior of the oven, the central disk 9 has an oxide layer 3 on both sides.

FIGS. 7 and 8 show schematic representations of the disc arrangements in the oven according to two

inventive embodiments. Preferably, the glass substrate 1 without coating has a light transmission Y measured with standard light C / 2 ° of more than 5%, preferably more than 20% and particularly preferably more than 80%. The light transmission Y is measured in the CIE color system. This value applies regardless of the thickness of the substrate, which can usually be between 2 and 10 mm. The substrate material may be transparent, transparent colored by color oxides or have a translucent appearance by light scattering. Such

Light scattering can e.g. in glass ceramic substrates or

Ceramic substrates by the presence of scattering

Crystals are generated in the substrate material.

In a preferred embodiment that consists

Substrate material of a silicate glass (Si0 ₂ content> 40 wt .-%). Advantageously, here is a floated

Glass pane made of a commercially available soda-lime glass used as a substrate. Such soda lime slices are available in various qualities, depending on the iron content. The soda lime glass pane is particularly preferably thermally prestressed. In a further preferred embodiment, it is a floated borosilicate glass, such as the floated glass types BOROFLOAT ^® 3.3 or BOROFLOAT ^® 4.0 from SCHOTT AG.

The embodiment shown in Fig. 7

differs from the structure shown in FIG. 6 in that the coating of the outer pane 8 has only one layer 2. The layer 2 in this case contains an IR-reflecting pigment with a TSR value of at least 20% and a remission at a

Wavelength of 1500 nm of at least 35%. Here, the layer 2 acts not only as a decorative layer, but

moreover enables an efficient backscattering of the heat radiation into the interior of the furnace so that an additional layer 3 with transparent conductive oxides can be dispensed with. In Fig. 8, a development of the invention is shown, in which also in the middle

Disk 8, the oxide layers 3 is replaced by the layer 2 according to the invention.

Measurements have shown that a substrate coated according to the invention is outstandingly suitable for use as an outer pane of a multi-pane oven door. For this purpose, a correspondingly coated

Substrate installed as an outer pane in an oven and the surface temperature on the outside of the

Glass pane detected (Fig. 14). The respective ones

Surface temperatures of the disks were determined in this case with an IR camera from the company Fluke, wherein at a distance of one minute a corresponding IR thermal image

has been recorded. The distance of the thermal imager to the outer pane of the oven door was here 203.2 cm.

From the thermal images thus obtained, the

determined corresponding temperatures. In the test setup, the volume of the oven was 28.317 1 and 5.3 ft ^3, respectively. The

Measurements were taken at an oven internal temperature of 875 ° F (468 ° C) and 475 ° F (246 ° C).

 In addition, comparative measurements were carried out using a glass substrate with an enamel coating 4 with a conventional black pigment as the outer pane.

In Fig. 15, a laboratory measurement setup is described. The respective surface temperatures of the disks were measured with a pyrometer 39 (impac, IE 120 / 82L).

with the focus point placed on the outside of the decorated pane and recording a corresponding reading every one minute. The distance of the pyrometer 39 to the outer disc of

The oven door was 50 cm. In the test setup, the volume of the oven was 30x12x12 cm ³ . The distance of the decorated pane to the oven was 2 cm the oven opening has a diameter of 3 cm. The measured slices are

Fully coated.

9 shows a schematic representation of the coverage of the outer pane of the exemplary embodiment with the respective decorative layer. The dimensions of the outer disc are each 29.0 by 20.1 inches. In the outer area of the disc was a with the respective decorative coating

full frame 15 is applied, the frame 15 leaves a viewing area 16 with the dimensions of 20 by 9.75 inches. In this viewing area 16 is the decorative layer applied in the form of a grid pattern 17. In addition, comparative measurements were carried out using a glass substrate with an enamel coating 4 with a conventional black pigment as the outer pane.

Figures 10 and 11 show schematically the respective construction of the oven door of the embodiment (FIG. 10) and the comparative example (11). In both cases the uncoated side of the substrate points outwards. The middle and the inner pane of the oven door are each coated on one side with a coating 3. The coating 3 contains transparent, conductive oxides.

After installing the respective panes, the oven was brought to an operating temperature of 246 ° C or 468 ° C and the temperature determined at various points on the outside of the outer oven disc.

Fig. 12 shows the recording of a thermal imaging camera an outer oven door, wherein the oven was heated to 468 ° C with an outer pane according to the invention after a period of operation of 180 minutes. The comparatively high temperatures at the upper edge of the door as well as in the lower one

Central area here are explained by a heat loss due to the experimental setup and also occur in the recording shown in FIG

Thermal imager of the comparative example.

In Fig. 14 is a variant of a measuring structure for

Determination of the outside temperature of the oven door shown schematically. This is a household standard oven with a volume of 28.317 1 or 5.3 ft ³ to 246 ° C.

(maximum operating temperature in baking mode) or 468 ° C (maximum operating temperature in pyrolysis mode) heated. The oven door has three in this measuring arrangement

Slices on, wherein the inner two glass sheets each have a low e-coating 3. The coatings 3 are in this case arranged on the facing surfaces of the two inner glass panes. Both

examined embodiments, the outer

Glass pane, a coating 2 comprising an IR-reflecting pigment, wherein the coating 2 is applied to the side of the glass sheet, which in the

Furnace interior shows. The respective surface temperatures of the disks were in this case determined with an IR camera 28 from the company Fluke, wherein at a distance of one minute, a corresponding IR thermal image was taken. The distance of the thermal imager to the outer pane of the

The oven door was 203.2 cm. From the thermal images thus obtained, the corresponding temperatures

determined. In the test setup, the volume of the oven was 28.317 1 and 5.3 ft ^3, respectively.

 In Fig. 15 is a schematic diagram of a measuring arrangement for

Determination of the surface temperatures of a coated glass sheet under laboratory conditions. Here, a laboratory furnace 31 is at a temperature of 450 ° C.

heated. The oven has an opening with a diameter of 3 cm. At a distance of 3 cm from this opening, the glass sheet 1 to be measured is placed with the coating 2, wherein the coating 2 in the direction of

Oven opening shows. The surface temperature of the

coated glass pane 1 is equipped with a pyrometer

(impac, IE 120 / 82L) 34 determined. The pyrometer 39 (here is behind the measured to be measured glass substrate 30 and at a distance of 50 cm to be measured

Glass pane 1 is arranged. FIGS. 16 and 17 show the temperature profile on the outside of different furnace doors as a function of the operating time, with the individual furnace doors differing only by the coating of the outer pane. The surface temperatures were determined by the measurement setup shown in FIG. 14, the oven temperature was 246 ° C. (FIG. 16) and 468 ° C. (FIG. 17).

Curve 11 here is to be assigned to the comparative example shown in FIGS. 10 and 12. The curves 12 to 15 and 18 and 19 are different

Embodiments that are in terms of their

Pigment content, the degree of coverage and the structure of the applied decoration and in Table 5

to be discribed.

The grid pattern has a diameter of 1 mm (small holes) with a total occupation level of the layer of 64% and 2 mm (big holes) with a total occupancy rate of the layer of 67%. The reference door has a grid pattern with a diameter of 1.5 mm with a total occupancy rate of 63%

Table 5 shows the layer compositions of

Embodiments according to the curves 12, 13, 14, 15, 18 and 19. The discs have here in the field of view a dot matrix with round, uncoated areas in the

Also referred to as holes on. In this case, dot grids or dot grids with different

Used hole sizes. In the dot matrix with small holes have the

uncoated areas, i. the holes in the

Coating, a diameter of 1 mm. The

Occupancy rate of the outside of the disc with the

Coating is 64% in this design variant.

For dot screens with large holes inside the

Dot rasters, the holes or the uncoated areas within the dot matrix have a diameter of 2 mm. Here, the outside of the disc has a

Occupancy rate of 67%.

In this case, both in FIG. 16 and in FIG. 17, curve 12 corresponds to the temperature profile of the sample 1 from FIG. 5, the applied decorative raster having large holes, curve 13 the temperature profile of the sample 10 from table 5, curve 14 the temperature profile of the sample 1 from Table 5, with the applied decorraster having small holes, curve 19a (only in Fig. 16) of sample 9 from Table 5, with the applied decorraster having large holes, curve

18 the temperature profile of the sample 4 from Table 5 and curve

19 the temperature profile of the sample 3 from Table 5.

Table 5: Embodiments and comparative examples of the temperature measurements shown in FIGS. 16 and 17

For all samples the temperature was measured in measuring range 15 (see Figures 12 and 13). Measuring range 15 represents the surface area with the comparatively highest temperature.

From Fig. 16 it is clear that in the

 Embodiments, the temperature in the measuring range rises sharply up to an operating time of about 60 minutes and then the temperature does not rise or only slightly. Here, in all embodiments, the

measured surface temperatures below the

corresponding temperatures of the comparative example.

Fig. 17 shows the temporal temperature profile at a furnace temperature of 468 ° C, i. the setting pyrolysis of the oven and thus simulates the temperature profile during a pyrolysis process. Here, too, the measured temperatures increase steeply within the first 60 minutes, and then approach a largely constant value. This value is at all

Embodiments below the temperature of

Comparative example. Even with an operating time of more than 160 minutes, the embodiments show a maximum temperature in the measuring range of less than 75 ° C and less than 165 ° F. On the basis of curves 12 and 14 is also visible that the heating of the disc at

coated slices with a high occupancy rate is lower than with corresponding slices with a lower occupancy rate. Curve 12 is one here To assign slices with a grid pattern, with which a higher occupancy rate can be achieved than with the

Design disc with temperature profile 14.

The slices of curves 12 and 19 differ in the pigment content in the coating. Curve 12 is assigned here to sample 1 and curve 19 to sample 3 from table 5. Surprisingly, Fig. 17 shows that

Coatings with pigment proportions of 20% by volume (curve 12) in the coating have a better temperature behavior than sample 3 (curve 19) with 30% by volume of pigment fraction. This can be explained by the fact that in the production of

corresponding coatings with high pigment content of the proportion of IR-reflecting pigments in the

corresponding coating is so high that when

Burning process a large part of the heat radiation through the IR-reflecting pigments are reflected in the paste and the heat thus not to melt the glass powder or to form a uniform flow of glass to

Available. This can be seen in the achieved

Scratch resistance of the baked layers. At 30% by volume of pigment, a 10N sclerometer test is just passed. This in turn can adversely affect the optical layer properties. Also the

Homogeneity of the layer or its mechanical or

Chemical resistance can be too high

Pigment content in the coating are adversely affected. The proportion of the pigment in the coating is therefore preferably 10 to 25% by volume, preferably 12 to 20% by volume. -%.

 Table 6: Determined temperatures of the embodiments shown in Table 5 in baking mode (246 ° F) and pyrolysis mode (875 ° F) Table 6 summarizes and gives the results of the temperature measurements shown in Figs. 16 and 17

Surface temperature of the disc after a heating time of 180 min at 246 ° C or at 468 ° C on. Samples 1, 3, 4, 9 and 10 correspond to samples 1, 3, 4, 9 and 10 listed in Table 5. The comparative sample is a standard oven door, i. with normal black pigments. From Table 6 shows that the embodiments have a better insulation effect

have as the standard door. So that is after 180

Minutes operating temperature measured surface temperature in the embodiments always below the

corresponding temperature of the standard oven door. this applies Both for a heating temperature of 475 ° F and 246 ° C, which simulates the baking process, as well as for a

Heating temperature of 875 ° F and 468 ° C, which corresponds to the temperature in the pyrolysis. It can thus be concluded from Table 6 that the IR-reflecting coating according to the invention has regard to its

Insulation effect is at least equal to the conventional coatings with transparent conductive oxides.

Fig. 18 shows the influence of various

 Glass compositions in the coating on the color locus of the coating determined with a D65 light source measured from the color side in accordance with the measurement standard EN ISO 11664-4. The samples of area 21 are coatings with a zinc-based glass matrix assigned to the samples of the

Area 20 have a bismuth-containing glass matrix. From Fig. 18 it is clear that coatings with

zinc-based glasses have a shift to yellow color locations while the coatings of the regime 20 are shifted to blue color locations.

Fig. 19 shows the in-line transmission profile

various embodiments (23 to 27) and the comparative example (22). In in-line transmission, only the light which passes through the sample at a forward scattered angle of 5 ° is directed to the detector, i. Scattering components are not displayed in the trace. It can be seen here that the in-line transmission, i. the embodiments below the transmission of Comparative Example 22 is located. Preferably, the

according to the invention coated substrates for the Wavelength range between 1.5 ym and 4.5 ym an in-line transmission of at most 0.01%.

In FIGS. 20 and 21, embodiments are schematically illustrated in which the coating 2 deposited on the glass 1 has pores 32 and 33, respectively. In both cases these are closed pores. Fig. 20 shows an embodiment with largely

spherical pores 32. Corresponding pores can be obtained, for example, by the use of calcium carbonate as a blowing agent. In contrast, the pores 33 shown in FIG. 21 have an elliptical cross section and thus an anisotropic structure. Pores with one

appropriate form, for example, by the

Use of rice starch as a blowing agent can be obtained.

It is possible that the pores are present in different sizes and shapes, that is, generally, without being limited to the example shown schematically here, also not round.

Fig. 22 and 23 show the temperature profile on the

Outside of different oven doors depending on the Operating duration of various embodiments, wherein the individual furnace doors only by the

Differentiation of outer pane coating. In FIGS. 22 and 23, a laboratory furnace was hereby placed on a

Temperature of 450 ° C heated and then with the measuring device shown in Fig. 15 the

Surface temperature of the coated glass as a function of the service life determined.

In FIG. 22, the measured maximum are here

FIG. 23 shows a fit obtained by averaging (logistic curve fit with 3 parameters) of the temperature profiles shown in FIG. 22.

The curves 13, 14 and 15 (As Sample 1, 9, 10, also

measured as a printed oven door, see above) correspond to temperature profiles of embodiments in which the IR-reflective coating is substantially free of pores, which are curves 34 to 37

 Assign temperature profiles of embodiments with porous IR-reflective coatings.

In Table 7, the individual embodiments are characterized in detail.

Table 7: Characterization of the samples shown in FIGS. 22 and 23

Samples 13 and 14 correspond to the embodiments shown in FIGS. 16 and 17. The coatings of these embodiments were made without the use of blowing agents. In contrast, samples 34 to 37 are porous coatings. In the

 To prepare these coatings, the blowing agents shown in Table 7 were used, which thus obtained

Coatings therefore have closed pores. All temperature profiles shown in Figs. 22 and 23 were obtained by using the measurement setup shown in Fig. 15. The respective coating compositions were applied to the substrate by screen printing using a 77/55 T screen.

From Fig. 23 shows that even after a one-hour operating time of the furnace at 450 ° C, the determined on the outside of the disc temperature is below 50 ° C. In the embodiments 34 to 37, in which the IR-reflecting pigments are present in an enamel with closed pores, this maximum temperature can be lowered again. It is assumed that the pores within the coating represent structures on which the IR radiation can be additionally scattered.

The expression of this positive effect on the maximum surface temperature of the disk is dependent on the structure of the pores. For samples 36 and 37 rice starch was used and for samples 34 and 35 CaC0 ₃ as

Blowing agent used. When using rice starch as the blowing agent, anisotropic pores having an ellipsoidal cross-section are preferably formed, while the use of CaCO ₃ as the blowing agent results in substantially spherical pores.

In this case, FIG. 23 shows that in the coated glasses 34 and 35, whose pores have a spherical or largely spherical structure, the insulating effect is higher than in the case of the coated glasses 36 and 37 whose coating has ellipsoidal or rice-shaped pores.

Furthermore, it is apparent from Fig. 23 that the proportion of the blowing agent in the paste is due to the IR reflection of the corresponding coating effects. Thus, samples 34 and 35 differ only in their content

Blowing agents. While the blowing agent content in the coating-producing paste 34 is 20% by volume, the corresponding paste for preparing the coating 35 contains only 10% by volume of CaCCd as the blowing agent. Here, the sample 35 has a better insulation effect than the sample 34, so that after an operating time of 180 minutes, the maximum temperature of the sample 35 is 0.8 ° C lower than the maximum temperature of the sample 34 among comparable

Conditions.

An excessive amount of blowing agent in the paste causes so many pores to be formed that they partially bond and open pores are formed. An indication of open pores and an associated uneven

Surface It is assumed here that

closed pores favor IR reflection.

Unless the substrate is transparent, not

volume-colored substrate is formed, is the

Barrier effect of the coating, for example, determinable in a test in which a drop of a fluid

Medium, e.g. Water is applied to the coating and then applied for at least 10 seconds and wiped off after exposure, wherein when looking through the coating through the substrate, the point of contact of the drop is not recognizable as such, if this test is passed.

Such test methods are generally known under the term of visual inspection and are based on the relevant standards, such as DIN EN 1330-10, DIN 25435-2 as well as DIN EN 13018. In the present case, a direct or indirect visual inspection is favored by an examiner. In the case of direct visual inspection, the test is carried out with the beam path uninterrupted between the eye of the tester and the surface to be tested, whereas in the case of a test

indirect visual inspection as a result of detection by the surface to be tested by suitable photographic or video technology, the beam path is interrupted. Furthermore, a

local visual inspection in accordance with DIN EN 13018, in which a minimum illuminance, a distance to the surface to be tested and a viewing angle of the tester are defined.

The minimum illuminance used in the test is at least 500 ix on the test surface at a distance of less than 600 mm. The

Viewing angle of the tester is at least 30 °. The examiner preferably complies with the relevant standards, such as DIN EN 13018 and EN 473

specified requirements.

Such a test method is therefore especially

preferred because it can be easily adapted to the respective fields of application of the coated glass-ceramic substrates. For example, the exposure time is usually selected as a function of the respective fluid medium considered and can also be more than 10

Seconds.

Fluids in the sense of the present disclosure preferably comprise liquids, in particular water, aqueous liquids, alcohols, on these liquids

based or comprising these fluids Liquids, such as window cleaners, and / or oils and water vapor.

A preferred procedure for carrying out a

Visual inspection by an examiner as explained above with the aim of the waterproofness or the

Moisture seal of a coating according to

The present disclosure comprises the following steps:

- Applying in particular a drop of a

 Liquid, in particular a drop, on an area on the surface of the coating of the

 Substrates,

 - Exposure of the liquid for a period of 15

 seconds

 - wipe off the residual moisture of the liquid with a dry cloth,

 Turning the substrate such that the coating is arranged on the side of the substrate facing away from the examiner, and

 Check by visual inspection whether a color change is detectable in the area or in an area adjacent to this area, where a) the visual inspection in daylight according to

 Standard illuminant D65 or under illumination such as a light bulb, energy saving lamp,

 Fluorescent lamp, or a light emitting diode,

b) the illuminance thereby amounts to at least 500 lx at a distance to the coating, ie to the test surface, of less than 600 mm, and c) the viewing angle of the tester is between 5 ° and 90 °, preferably at least 30 °, wherein when the coating is viewed through the substrate, the point of contact of the droplet is not disturbingly visible and, in particular, is not recognizable as such.

The above-mentioned visual inspection, also referred to as "sidolein test" in the above table, comprises in particular the test as to whether a water edge and / or a water spot is from the coated side

opposite side of the substrate is visible from. As the test liquid, window cleaner was used in the test listed in the above table.

As very good in the present case, a layer

described, which shows after the test, neither on the front nor on the back of a color change. In the present case, a layer which shows no color change after the test on the front side and shows a wipeable edge on the back is described as good.

 Another way, the IR reflectivity of the

To increase coating consists in increasing the

Layer thickness, for example, by a multiple application of the corresponding paste or suspension on the substrate. FIG. 24 shows the influence of the layer thickness of the applied coating on its IR reflectivity.

Here were the samples 14 (unfoamed coating for comparison), 34 and 38 by screen printing under

Using a 77T screen applied to the substrate. The coatings of samples 14 and 34 were applied as a single print, the coating of the sample 38 was as a double print by two printing operations on the Substrate brought. The samples 34 and 38 differed only by the number of printing operations. It can be seen here that by increasing the layer thickness the maximum temperature can be reduced by more than 2 ° C. The following table will show more

Measurement results described. Here, the number of completed printing operations (single or double pressure) and the maximum temperature determined on the outside of the disk with the measuring arrangement shown in FIG. 15 are listed after 60 minutes of operation of the furnace at a temperature of 450 ° C.

Claims

claims

1. paste for making an IR-reflective

 Layer, especially on a glass or

 A glass-ceramic substrate comprising at least one IR-reflecting pigment and glass powder, wherein the IR-reflecting pigment has a TSR value determined according to ASTM G 137 of at least 20% and at a wavelength of 1500 nm a remission measured according to ISO standard 13468 of at least 50%.

2. A paste according to claim 1, wherein the glass powder

 Particles having a size distribution with a d50 value of less than 3 ym and greater than 0.1 ym, preferably less than 2 ym and greater than 0.1 ym.

3. A paste according to any one of the preceding claims wherein the glass powder contains zinc oxide and / or bismuth oxide, preferably 0.1 to 70 wt .-% zinc oxide, preferably 0.1 to 30 wt .-% zinc oxide and / or 0.1 to 70 wt Bismuth oxide, preferably 8 to 70% by weight of bismuth oxide.

4. Paste according to one of the preceding claims,

 wherein the glass powder has the following composition in% by weight:

wherein particularly preferably the glass powder at least 1 wt .-% of at least one alkali metal oxide selected from the group of Na ₂ 0, Li ₂ 0 and K ₂ O or mixtures of these oxides and / or at least 1 wt .-% of at least one further oxide selected from Group of CaO, MgO, BaO, SrO, ZnO, Zr0 ₂ , and Ti0 ₂ includes.

5. A paste according to any one of the preceding claims 1 to 3, wherein the glass powder has the following composition in% by weight:

wherein the glass powder particularly preferably at least 1% by weight of at least one alkali metal oxide selected from the group of Na _2Ü , Li ₂ 0 and K ₂ O or mixtures of these oxides and / or at least 1 wt .-% of at least one further oxide

 selected from the group of CaO, MgO, BaO, SrO, ZnO,

ZrÜ ₂ , and TiÜ ₂ , includes.

6. Paste according to one of the preceding claims,

wherein the IR-reflecting pigment comprises particles having a size distribution with a d50 value in the range from 0.5 μm to 2 μm, preferably in the range from 0.8 μm to 1.8 μm.

Paste according to any of the preceding claims, wherein the IR-reflecting pigments have particles with a specific surface area in the range from 1.1 to 8 m ² / g, preferably in the range from 1.8 to 3.5 m ² / g.

8. Paste according to one of the preceding claims,

 wherein at least one IR-reflecting pigment has a TSR value determined according to AST G 173 of at least 25% and / or at a wavelength of 1500 nm has a reflection of at least 60% and particularly preferably of at least 70%.

9. Paste according to one of the preceding claims,

 wherein the paste comprises a chromium-containing IR-reflecting pigment, preferably a chromium-containing iron oxide, a chromium-containing hematite and / or a chromium-containing spinel.

10. A paste according to any one of the preceding claims, wherein the content of conductive oxides in the paste, in particular conductive oxides selected from the group comprising the elements indium tin oxide, fluorine-tin oxide, aluminum-zinc oxide and antimony tin oxide smaller 500 ppm.

11. A paste according to any one of the preceding claims, comprising 10 to 40 wt. % IR-reflecting pigments, 45 to 85% by weight of glass powder and / or 12 to 35% by weight of screen printing medium.

12. A paste according to any one of the preceding claims, comprising 7 to 43% by volume of IR-reflecting pigments, 35 to 50% by volume of glass powder and / or 30 to 50% by volume of screen printing medium.

13. A paste according to any one of the preceding claims, comprising at least one further, second IR-reflecting pigment, wherein the paste is preferably a second IR-reflecting pigment

 Cobalt chromite spinel, an indium manganyttrium oxide, a niobium fumed tin zinc oxide, a tin zinc titanate and / or a cobalt titanate spinel.

14. A paste according to the preceding claim, wherein the proportion of the second IR-reflecting pigment in the paste 0.5 to 15 wt .-%, preferably 3.5 to 12.5 wt .-% is and / or the volume ratio between the Volume of the second pigment to the volume of the first pigment in the range of 0.03 to 0.6, preferably in the range of 0.05 to 0.56 and particularly preferably in the range of 0.14 to 0.47.

A paste according to any preceding claim, wherein the paste comprises a blowing agent.

A glass or glass-ceramic substrate comprising a surface area having a coating comprising a glass matrix and IR-reflecting pigments, wherein the IR-reflecting pigments have a TSR value of at least 20% determined according to ASTM G 173 and the coating at a wavelength of 1500 nm nm has a reflectance measured according to ISO 13468 of at least 35%.

17. Glass or glass-ceramic substrate according to the

 preceding claim, wherein the coating in the entire wavelength range of 1500 nm to 2500 nm has a remission of at least 35%, preferably of at least 40% and particularly preferably of at least 45%.

18. glass or glass-ceramic substrate according to one of the two preceding claims, wherein the coating at a wavelength of 1500 nm, a remission of at least 35%, preferably at least 40% and most preferably at least 45%.

19. Glass or glass-ceramic substrate according to one of the two preceding claims, wherein the IR-reflecting pigments particles with a

 Size distribution with a d50 value in the range of 0.5 ym to 2 ym, preferably in the range of 0.8 ym to have 1.8 ym.

20. Glass or glass-ceramic substrate according to one of the preceding claims, wherein the IR-reflecting pigments particles having a specific surface in the range of 1.1 to 8 m ² / g, preferably in the range of 1.8 to 4.5 m ² / g have.

21. Glass or glass ceramic substrate according to one of the preceding claims, wherein the IR-reflecting pigments have a TSR value determined according to ASTM G 173 of at least 25%.

22. Glass or glass-ceramic substrate according to one of the preceding claims, wherein the coating a chromium-containing IR-reflecting pigment, preferably a chromium-containing iron oxide, a chromium-containing hematite and / or a chromium-containing spinel comprises.

23. glass or glass ceramic substrate according to any one of the preceding claims, wherein the content of

 conductive oxides in the coating, in particular on conductive oxides selected from the group comprising the elements indium tin oxide, fluorine-tin oxide,

 Aluminum-zinc oxide and antimony-tin oxide is less than 500 ppm.

24. glass or glass ceramic substrate according to one of the preceding claims, wherein the coating comprises closed pores, wherein the coating is formed as a barrier to the entry and passage of fluids and a barrier effect unfolds.

25. glass or glass ceramic substrate according to

 preceding claim, wherein the coating is formed as a high-temperature-stable coating, in particular for temperatures> 400 ° C.

26. glass or glass ceramic substrate according to one of the two preceding claims, wherein the coating is substantially inorganic, comprising in particular glass frits, pigments and / or pores.

27. Glass or glass-ceramic substrate according to one of the three preceding claims, wherein the resulting coefficient of thermal expansion of the coating and the thermal expansion coefficient of the substrate from each other by no more than 4 * 10 ⁶ / K in

 Temperature range from 20 ° C to 700 ° C differ.

28. Glass or glass ceramic substrate according to one of the preceding claims 24 to 27, wherein the

 Coating has a thickness between at least 0.1 ym and at most 500 ym, preferably between at least 1 ym and at most 100 ym, more preferably between at least 1.5 ym and at most 50 ym.

29. Glass or glass-ceramic substrate according to one of the preceding claims, wherein the substrate is a

 Soda lime glass or a borosilicate glass.

30. Glass or glass ceramic substrate according to one of the preceding claims, wherein the substrate is a

 thermally toughened glass is.

31. glass or glass ceramic substrate according to any one of the preceding claims, wherein the glass matrix of the coating bismuth oxide, preferably 8 to 70 wt .-% bismuth oxide and / or zinc oxide, preferably 0.1 to 0 wt .-% zinc oxide.

32. Glass or glass-ceramic substrate according to one of the preceding claims, wherein the glass matrix of the coating has the following glass composition in% by weight:

S i0 ₂ 30 - 75 preferably 44-75

 AI2O3 0-25 preferably 0.2-25,

more preferably from 2-25 B2O3 0-30 preferably 1-30, more preferably 5-30

Li ₂ 0 0-12

Na ₂ 0 0-25 prefers 0-15

 CaO 0-12

 MgO 0-9

 BaO 0-27

 S rO 0-4

 ZnO 0-35 prefers 0-20

Bi ₂ 03 0-5

T i0 ₂ 0-10 preferably 0-5

Z r0 ₂ 0-7

AS ₂ 0 ₃ 0-1

Sb ₂ 03 0-1.5

 F 0-3

 CI 0-1 prefers 0

H ₂ 0 0-3.

33. Glass or glass ceramic substrate according to one of

 preceding claims 16 to 31, wherein the glass of the glass matrix of the coating has the following composition in wt .-%:

Si0 ₂ 6-65, preferably 10-65, more preferably 15-65

A1 ₂ 0 ₃ 0-20

B ₂ 0 ₃ 0-40, preferably 1-30, more preferably 3-30

Li ₂ 0 0-12

Na ₂ 0 0-18

K ₂ 0 0-17

 CaO 0-17

 MgO 0-12

 BaO 0-38

SrO 0-16

34. Glass or glass ceramic substrate according to one of the preceding claims, wherein the proportion of the IR-reflecting pigment in the coating 15 to 55 wt .-%, preferably 15 to 45 wt .-% and / or the proportion of the glass matrix in the coating 45th to 85 wt .-% is.

35. Glass or glass ceramic substrate according to one of the preceding claims, wherein the coating comprises at least a first and a second IR-reflecting pigment and the coating preferably as a second IR-reflecting pigment, a cobalt chromite spinel, an indium manganittrium oxide, a Niobiumschwefelzelzinnzinkoxid, a Zinnzinktitanat and / or Cobaltittanatspinell contains,

and / or the content of the second IR-reflecting pigment in the coating is 0.75 to 18.5% by weight, preferably 4.5 to 14% by weight.

36. Glass or glass-ceramic substrate according to one of the preceding claims, wherein the layer thickness of the coating 3 to 35 ym, preferably 8 to 35 ym and particularly preferably 10 to 20 ym.

37. Glass or glass-ceramic substrate according to one of the preceding claims, wherein the coating on at least one surface of the glass or

 Glass ceramic substrate is applied laterally structured.

38. glass or glass-ceramic substrate according to

 preceding claim, wherein at least 60%, preferably at least 63% and particularly preferably at least 65% of at least one of the glass surfaces with the

 Coating are coated.

39. Glass or glass-ceramic substrate according to one of the two preceding claims, wherein the coating laterally structured in the form of a lattice or

 Dot matrix is applied to at least one of the glass surfaces.

40. Glass or glass-ceramic substrate according to one of the preceding claims, wherein the coating

 is applied directly on the substrate surface and / or the substrate no additional coating containing conductive oxides, preferably none

containing conductive oxides from the group comprising the elements indium tin oxide, fluorine-tin oxide, aluminum-zinc oxide and antimony tin oxide.

41. Household appliance, in particular oven, comprising a glass or glass-ceramic substrate according to one of the preceding claims 16 to 40.

42. Baking oven door a disc assembly comprising at least two panes as an outer disc

 Glass substrate according to one of claims 16 to 40.

43. Baking oven door according to the preceding claim,

 wherein the glass substrate is provided on one side with the coating, the coated side of the

 Glass substrate in the direction of the furnace interior shows and at least 60%, preferably at least 65% and more preferably at least 70% of the surface of the glass substrate are covered with the coating.

44. Baking oven door according to one of the two preceding claims, wherein the outer pane has no further coating with conductive oxides.

45. Baking oven door according to one of the two preceding claims comprising at least three glass panes, wherein the outer glass pane and the central glass pane glass substrates according to one of claims 16 to 40 comprise.

46. Baking oven door according to the preceding claim,

wherein the middle glass pane comprises a glass substrate which is provided on both sides with a coating according to one of claims 16 to 39 comprising an IR-reflecting pigment and a glass matrix.

47. Kaminsichtscheibe comprising a

 Glass-ceramic substrate according to one of Claims 16 to 40.

48. Process for the preparation of a glass or

 Glass-ceramic substrate comprising a

 Surface area with a glass matrix and IR-reflecting pigments, in particular for

 Production of a glass or glass ceramic substrate according to one of claims 16 to 40, comprising

 at least the following steps: e) providing a glass or

Glass ceramic substrate, f) providing a paste comprising a glass powder with a softening temperature Ewciaspuiver, wherein Ew _Giaspuiver below the

 Deforming temperature of the substrate material is at least one IR-reflective

 G) laterally structured application of the paste provided in step b) to the glass or glass-ceramic substrate provided in step a) by means of screen printing, h) baking applied in step c)

Layer at temperatures in the range of T _Einbranci O Tgoiaspulver

49. The method according to the preceding claim, wherein in step a) a glass substrate, preferably a

 Soda lime glass or borosilicate glass ready

 and the glass substrate in step d) together with the baking in step c).

 applied layer is thermally biased.

50. The method according to the preceding claim, wherein in step d) the temperature T _Einbranci in the range of 500 to 1000 ° C, preferably in the range of 500 to 700 ° C.

51. The method according to claim 48, wherein in step a) a crystallizable green glass as substrate

 is provided and in step d) together with the penetration of the layer, the ceramization of

 Green glass is done.

52. The method according to any one of the preceding claims 48 to 51, wherein in step d) the penetration of the in

Step c) layer applied preserving the structure.