DE102016103524A1 - Coated glass or glass ceramic article - Google Patents

Abstract

A process for producing a glass or glass ceramic article (1), comprising the steps of - providing a flat glass or glass ceramic substrate (2) with two opposite side surfaces (20, 21), which - in the visible spectral range of 380 nm to 780 nm, a light transmission τvis of at least 1%, preferably at least 30%, of visible light passing through the glass or glass-ceramic substrate (2) from one side surface to the opposite side surface, wherein - a side surface of the glass or glass-ceramic substrate (2) having an opaque coating (5) which has a light transmission τvis of not more than 5% in the visible spectral range from 380 nm to 788 nm, wherein - a pulsed laser beam is directed onto the opaque coating (5) and the coating (5) is ablated several times at different locations locally up to the Surface of the glass or glass ceramic article removed and thus a perfori In this way, the opaque area coating of a plurality of openings in the opaque coating (5) is produced such that the opaque coating becomes partially transparent in the area (10) of the grid.

Description

The invention generally relates to glass or glass ceramic articles which are provided with an opaque coating. In particular, the invention relates to such articles, which are provided with luminous display elements or provided for a device with luminous display elements.

Glass ceramic hobs are known from the prior art, which are coated on its underside to change the appearance, as well as to hide under the glass ceramic parts of the cooker.

One possibility for this is sol-gel coatings. These are quite temperature resistant and are also characterized by good adhesion to the glass ceramic plate. To cover the inner parts of a cooker, opaque coatings are typically used.

For some applications, it is desirable if the coating is not full-surface, but has windows. Such windows are arranged, in particular, in front of luminous display elements, so that these display elements shine through the glass ceramic plate and are visible to an operator viewing the useful side of the hob. In part, these windows are covered by translucent coatings to improve the aesthetic impression. With the same color, this creates a homogeneous surface.

In the case of cooktops today, symbols, signs or other logos and designs are printed by screen printing. However, it is difficult here to produce very fine structures, such as thin lines.

In addition, the screen printing in very fine areas or runs of lines, the reproducibility due to the screen printing fabric is difficult. Furthermore, for each new product request / design change, the production of a new screen is necessary, which means setup costs are very high, which is particularly noticeable in small series. Making individual designs for each end customer is therefore expensive.

In the case of multilayer coatings, the problem with a printing technique such as screen printing is that a congruent structuring is difficult here. Therefore, in the case of multilayer coatings, a larger window in one of the coating layers is usually left open here, and a further coating layer in the region of the window more accurately patterned with the desired pattern. However, the window can be visible, in particular in the case of luminous display elements, if the more precisely structured coating layer is not completely opaque to light.

The EP 0 868 960 B1 proposes a method for the production of control panel signs, in particular for household electrical appliances, in which at least one personalized laser engraving is produced on at least one screen print which has already been applied to a glass base shield blank by decors, symbols or corresponding characters in the screen printing layer attaches and then by covering these engravings by manual or automated application with a layer of different color, which can be done immediately after the engraving step or in a separate operation.

Like in the DE 10 2015 102 743.7 described by the applicant, can be generated with very thin cut lines or points (<40 microns) in a paint layer lighting applications in cooking surfaces that show a so-called dead-front effect, so are not visible when the light source is switched off with the eye. Such fine structures can be produced particularly well by laser ablation of color layers on transparent glass substrates. Due to the fineness of the structures, however, there is simultaneously a high requirement for the accuracy of the positioning of luminous elements. Especially with multi-elements, ie several light applications on a board, which are very close together, it can lead to unsightly light skipping or unlighted areas.

For conventional screen printing, special colors, so-called translucent colors, have been developed for this purpose. With these colors, larger, cohesive, exposed areas can be reprinted in a color layer, in which light elements can be arranged more easily. The translucent colors prevent the viewing under the glass plate, but let the light of the light elements through. In their production, as well as in the processing, however, they are expensive and produce by the changed composition a different color impression in plan view than the first printed, opaque base color.

The object of the invention is therefore to provide a method for producing a glass or glass ceramic article which has the desired optical properties, but is cheaper to manufacture compared to the use of the screen printing process.

This object is solved by the subject matter of the independent claims. Advantageous developments of the invention are specified in the respective appended claims.

• – Bereitstellen eines flächigen Glas- oder Glaskeramiksubstrats mit zwei gegenüberliegenden Seitenflächen, welches
• – im sichtbaren Spektralbereich von 380 nm bis 780 nm eine Lichttransmission τ_vis von mindestens 1%, bevorzugt mindestens 30% für sichtbares Licht aufweist, welches das Glas- oder Glaskeramiksubstrat von einer Seitenfläche zur gegenüberliegenden Seitenfläche durchquert, wobei
• – eine Seitenfläche des Glas- oder Glaskeramiksubstrats mit einer blickdichten Beschichtung versehen wird, welche im sichtbaren Spektralbereich von 380 nm bis 788 nm eine Lichttransmission τ_vis von höchstens 5% aufweist, wobei
• – ein gepulster Laserstrahl auf die blickdichte Beschichtung gerichtet und durch Ablation die Beschichtung mehrfach an verschiedenen Stellen lokal bis zur Oberfläche des Glas- oder Glaskeramikartikels entfernt und damit ein einen perforierten Bereich bildendes Raster einer Vielzahl von Öffnungen in der blickdichten Beschichtung hergestellt wird, derart, dass die blickdichte Beschichtung im Bereich des Rasters teiltransparent wird.

Accordingly, the invention provides a method of making a glass or glass ceramic article comprising the steps

• - Providing a flat glass or glass ceramic substrate with two opposite side surfaces, which
• In the visible spectral range from 380 nm to 780 nm has a light transmission τ _vis of at least 1%, preferably at least 30% for visible light, which traverses the glass or glass ceramic substrate from one side surface to the opposite side surface, wherein
• A side surface of the glass or glass-ceramic substrate is provided with an opaque coating which has a light transmission τ _vis of not more than 5% in the visible spectral range from 380 nm to 788 nm, wherein
• A pulsed laser beam is directed onto the opaque coating and the coating is ablated several times at various locations locally to the surface of the glass or glass ceramic article to produce a perforated region of a plurality of apertures in the opaque coating, such that the opaque coating in the region of the grid is partially transparent.

According to the invention, the grid is preferably formed from points that are arranged at a point distance from each other and have a point size.

The dot pitch here is less than 200 μm, preferably less than 150 μm, particularly preferably less than 100 μm.

The spot size is smaller than 30 μm, preferably smaller than 20 μm.

If the dot pitch and size are selected as described, the perforated area will look like a translucent color, allowing for larger positioning tolerances for light elements. Such areas provide advantages in laser-released symbols. Namely, the symbols are not defined by the ablated area in the color, but by the light element itself. If necessary, several products with different symbolics can be addressed in this way with a glass plate.

Another process parameter for the method according to the invention is the proportion of the ablated area on the total area. This proportion is described by the ratio of ablated area and unprocessed area within a perforated, partially transparent area. The inventors have found that areas with an ablated area fraction greater than 0.5% of the total area develop a different color impression. The ratio of ablated area and unprocessed area is calculated according to the formula (πr ² · 100%) / (a ² ), where r is the radius of a point and a is the distance between two points. Such areas appear brighter or darker to the viewer depending on the underlying color system. However, areas with less than 1% area coverage, especially below 0.5% of the total area, are of little interest since light applications appear slightly pixelated. In order to obtain a region with the highest possible resolution, surfaces with an ablated area fraction of more than 0.8%, preferably more than 1%, particularly preferably more than 1.5%, are therefore to be selected. In order to mitigate or eliminate the different color impression, a transition region has been developed in which the ablated area fraction between the base surface and the unablated region is <2% / mm, preferably <1% / mm, especially <0.5% / mm is reduced to less than 0.5% of the total area.

Therefore, a method is also within the scope of the invention in which a transition region is developed at the edge of the perforated region, in which further points are ablated so that the area fraction is less than 0.5% of the total surface area.

Such area shares can be realized with smaller openings or by larger distance of the openings.

Following the step of perforating, a cleaning step may be performed.

In particular, this cleaning step can take place by means of an adhesive roll.

The step of cleaning may be followed by a process step in which the perforated area is provided by means of a sealing layer, preferably with a transparent sealing layer. In a particular embodiment, the transparent sealing layer may be colored, preferably with dyes and / or pigments.

The material of the glass or glass-ceramic substrate can be selected such that the ablation threshold of the material of the glass or glass ceramic article in the infrared spectral range, in particular at a wavelength of 1064 nm or 532 nm, is higher than the ablation threshold of the opaque coating.

Furthermore, it is advantageous if the opaque coating is chosen such that it comprises a matrix of an oxide network with decorative pigments embedded therein. It is likewise advantageous if the matrix is produced from a sol-gel material which, after curing, is crosslinked in an inorganic or organic / inorganic manner.

Within the scope of the invention is also a glass or glass ceramic article which has been produced by means of the method according to the invention. Such a glass or glass ceramic article has a glass or glass ceramic substrate with two opposing side surfaces, wherein a side surface of the glass or glass ceramic substrate is provided with an opaque coating which has a light transmission τ _vis of not more than 5 in the visible spectral range from 380 nm to 780 nm %, and wherein a portion of the opaque coating is provided with a grid of apertures permitting the passage of light incident on the surface of the coating through the coating and the glass or glass ceramic substrate such that the area appears partially transparent, the dot pitch the openings is less than 200 microns, preferably less than 150 microns, more preferably less than 100 microns.

According to the invention, such a glass or glass ceramic article can form the operating surface of a household appliance. In this case, at least one luminous element is arranged in the interior of the household appliance, so that light emitted by this luminous element falls onto the openings in the opaque coating and can traverse the openings and the substrate.

In such a household appliance, the opaque coating may be applied to the inner side of the glass or glass ceramic article.

The domestic appliance according to the invention has at least one light-emitting diode or a laser diode as the light-emitting element.

Such a household appliance may also have a diffuser or a side-emitting light guide for distributing the light emitted by the luminous element through the perforated region.

Another application for a glass or glass ceramic article according to the invention is its use as a component of interior linings of cars, this component also having at least one light-emitting diode or a laser diode. The opaque coating points into the interior of the vehicle.

The invention will be described in more detail below with reference to the accompanying figures. In the figures, like reference numerals refer to like or corresponding elements. Show it:

1 a coated glass or glass ceramic article,

2 a device for laser ablation for the production of a glass or glass ceramic article according to the invention,

3 a glass or glass ceramic article produced by the method,

4 a glass-ceramic hob with a glass-ceramic article according to the invention as a cooking plate,

5 an embodiment with a side emitting light guide for illuminating the dot matrix, and

6 a further education in 3 illustrated embodiment.

In order to produce a glass or glass-ceramic article according to the invention, a flat or disc-shaped glass or glass-ceramic substrate is first of all produced 2 provided. The glass or glass ceramic substrate 2 thus has two opposite side surfaces 20 . 21 on.

One of the side surfaces, in 1 shown example, the side surface 20 , comes with an opaque or opaque coating 5 Mistake.

Particularly preferred coatings 5 are inorganic and / or inorganic-organic modified sol-gel layers. The oxidic network can preferably consist of SiO ₂ , TiO ₂ , ZrO ₂ , Al ₂ O _{3 building} blocks. In this case, organic radicals may still be present in the network.

In particular, coloring pigments in the form of metal oxides, in particular cobalt oxides / spinels, cobalt-aluminum spinels, cobalt-aluminum-zinc oxides, cobalt-aluminum-silicon oxides, cobalt-titanium spinels, cobalt, can be added as pigments Chromium spinels, cobalt-aluminum-chromium-oxides, cobalt-nickel-manganese-iron-chromium-oxides / -spinels, cobalt-nickel-zinc-titanium-aluminum-oxides / -spinels, chromium-iron-nickel-manganese Oxides / spinels, cobalt-iron-chromium oxides / spinels, nickel-iron-chromium oxides / spinels, iron-manganese oxides / spinels, iron oxides, iron-chromium oxides, iron-chromium Tin-titanium oxides, copper-chromium spinels, nickel-chromium-antimony-titanium oxides, titanium oxides, zirconium-silicon-iron oxides / spinels.

Preferred pigments are absorption pigments, platelet- or rod-shaped pigments, coated effect pigments, for. On mica basis. Likewise, pigments such as carbon black, graphite and dyes come into consideration.

Likewise, the layers (decorative / sealing layers) may contain further constituents such as fillers, preferably nanoscale fillers. Suitable fillers are, in particular, SiO _x particles, aluminum oxide particles, fumed silicas, soda-lime particles, alkali aluminosilicate particles, polysiloxane beads, borosilicate glass beads and / or hollow glass beads.

Such coatings are very durable and temperature resistant and can be produced depending on the choice of decorative pigments in a virtually unlimited number of different optical appearances. For this particular, the structuring of such coatings is a difficulty, especially if a high pigment content is present, or the individual pigment particles are relatively large. The latter is the case, for example, when platelet-shaped decorative pigments are used to produce metallic or glitter effects. When producing the openings or holes, the method according to the invention can even cut through the individual pigment particles and cut them clean.

The decorative pigments and their amount in the coating composition are selected so that at the intended layer thickness of the coating 5 whose transmission in the visible spectral range is less than 5%. Optionally, this low transmission can also be achieved by a multilayer coating.

Suitable coating compositions and coatings made therefrom are known, inter alia, from DE 10 2008 031 426 A1 , as well as the DE 10 2008 031 428 A1 known, the disclosure of which is fully made in this regard also the subject of the present application. Accordingly, in the invention, an opaque coating 5 are prepared by the decorative layer is prepared by a sol-gel process in a first step, wherein the layer is applied to the glass or glass ceramic substrate and cured by baking, and in a second step, the decorative layer is covered with a sealing layer , which is also prepared by a sol-gel process, wherein inorganic decorative pigments and fillers are mixed with a sol, the inorganic decorative pigments comprising platelet-shaped pigment particles and inorganic solid lubricant particles in a ratio in the range of 10: 1 to 1: 1 wt .-%, preferably 5: 1 to 1: 1 wt .-% and particularly preferably 3: 1 to 1.5: 1 wt .-% are added, and the mixture produced on the glass-ceramic substrate with the hardened decorative layer applied and then cured at elevated temperatures. The cured sealing layer can have the same composition as the cured decorative layer 5 , with the difference that the metal oxide network of the sealing layer contains more, based on the number of organic radicals, preferably at least 5% more organic radicals than the metal oxide network of the decorative layer. Under a metal oxide network is also a understood oxidic network with semiconducting elements in elemental form (in particular, therefore, the already mentioned SiO ₂ network).

Other than described above, however, other sealing layers may be used. For example, in addition to the sol-gel sealant layers described above, silicone layers or silicone-based layers are also suitable for sealing an underlying coating. Likewise, sealing layers based on organic polymers such as polyurethanes, polyacrylates, etc. are possible. The sealant layers may be pigmented.

The sealing layers may be transparent, colored transparent, translucent or opaque. Preference is given to pigmented sealing layers.

Also, on the side surface, ceramic colors specially adapted to the requirements of a ceramic bottom coating can be used. A preferred embodiment of this invention are hybrid layers, as in DE 10 2012 103 507 A1 described.

After making the coating 5 Now, by means of a device for laser ablation, a plurality of openings or holes 9 produced, the total of a perforated area 10 form. An example of such a device 11 shows 2 ,

The device for laser ablation 11 includes a laser 71 and a device to that of the laser 71 generated laser beam 7 over with a coating 5 coated side surface 20 of the glass or glass ceramic substrate 2 respectively. As a device for guiding the laser beam 7 over the surface, for example, a galvanometer scanner 15 be used.

In some applications, in addition to perforation, it is desirable to leave long straight lines, such as cooking surfaces, where these lines are used to delineate the cooking area or mark a cooking zone. For long, straight lines, the use of a polygon scanner is an advantage, as it can lead to small misalignment when stitching long lines. Due to the offset, the line becomes wider at the transition point and thus has the appearance of being significantly lighter in the transmitted light at this point.

As in 2 illustrated, but alternatively or in addition to a galvanometer scanner but also means for moving the glass ceramic element 1 be provided. In particular, an XY table is suitable for this purpose 16 , also known as a cross table. In this embodiment, the laser beam 7 arrested and the openings 9 in the desired shape by moving the XY table with the glass or glass ceramic substrate placed thereon 2 in the coating 5 be inserted.

Preferably, the openings or holes have the shape of circular points. The openings may also have the shape of elongated ovals. Other geometries are conceivable, for. B. parallel lines.

In the case of point-shaped openings these points in their entirety form a dot matrix. The distance between the individual points should be below 200 .mu.m, preferably below 150 .mu.m, more preferably below 100 .mu.m. The spot size is less than 30 μm, preferably less than 20 μm.

To maintain high accuracy, a synchronized scanner and motion device can also be used. Thereby the movement of the table becomes 16 or another, the substrate 2 moving device with the deflection of the scanner, such as the galvanometer scanner 15 synchronized.

To the laser beam 7 To focus on achieving the highest possible intensity on the surface, a suitable focusing optics 19 be provided. At the in 2 As shown, this focusing optics is the galvanometer scanner 15 downstream. It will be apparent to those skilled in the art, however, that other configurations suitable for the laser beam are possible 7 on the glass ceramic element 1 to focus. An arrangement of the focusing optics in the beam direction behind the galvanometer scanner is favorable in order to achieve short focal lengths. Generally, regardless of the specific structure of optics and motion mechanics, as the example of 2 shows, a focusing optics, in particular a lens or lens group or a focusing mirror with a focal length of less than 300 mm is preferred.

To the coating 5 to remove locally and thus an opening 9 through the coating 5 to create, the laser beam 7 moved with the means for guiding the laser beam over the surface, wherein the laser 7 is set so that the ablation threshold of the material of the coating 5 exceeded and thus the coating is removed at the place of impact. However, the laser power is adjusted so that the ablation threshold of the carrier material, ie the material of the glass or the glass ceramic of the substrate 2 is not achieved and so only the coating is removed. As an example, the glass ceramics marketed under the names Robax and Ceran Cleartrans may be mentioned. In these glass-ceramics, the ablation threshold for a laser wavelength of 1064 nm is about 5.2 × 10 ¹⁷ W / m ² .

In general, without being limited to the specific embodiment discussed above, it is thus advantageous if the materials of the glass or glass-ceramic material and the opaque coating are chosen such that the ablation threshold of the material of the glass or glass-ceramic substrate 2 especially in the infrared spectral range, particularly preferably at a wavelength of 1064 nm, is higher than the ablation threshold of the opaque coating 5 ,

Furthermore, it is generally favorable if the layer thickness of the opaque coating is not excessively large. On the one hand, this facilitates ablation by means of laser ablation. On the other hand, this is also favorable for the transmission of light through the openings 9 in the area 10 in the coating. If the coating is too thick, the walls are the openings 9 correspondingly long and swallow unnecessarily much light. It is therefore generally preferred if the opaque coating 5 a layer thickness of at most 300 microns, more preferably of at most 160 microns, more preferably of at most 50 microns.

Conversely, too thin coatings are unfavorable, especially with regard to adequate light blocking. Layer thicknesses of more than 3 μm, preferably at least 5 μm, are preferred. The above details of the minimum and maximum thickness are average values of the layer thickness.

The device for guiding the laser beam is by means of a control device 13 driven. On this example, run a program that translates the shape and location of the structural element in control signals, with which the laser beam 7 is moved over the surface by means of the device for guiding the laser beam. Preferably, the controller also controls the laser 7 , in particular with regard to a switching on and off and the laser intensity.

In one embodiment, a pulsed laser has been used 71 chosen, which can be focused sufficiently well to remove points of said dimensions. This was achieved with a neodymium YAG laser with a wavelength of 1064 nm and a pulse length of 10 ps. A scanner with an optic with a focal length of 255 mm was used. The M ² factor is less than 1.4, preferably less than 1.2. The pipe jet had a diameter of 12 mm. The average power W50 at 200 kHz was reduced to about 4W. Other lasers are also possible. Here, especially a laser with a wavelength of 532 nm and a pulse length of> 1 ns advantageous because the smaller wavelength better focus is adjustable and the length of the pulse length, the material is not dyed at the same time, which is disadvantageous in bright colors. Furthermore, lasers in the ns range have a significant cost advantage over lasers in the short ps range. However, it is advantageous in any case if the width of the ablated structures is less than 0.025 mm.

3 shows schematically in cross section a glass or glass ceramic article produced by the method according to the invention 1 , In the opaque coating 5 is an opening 9 inserted. This has a width 91 at the bottom of the coating 5 , or at the substrate surface exposed in the opening of at most 30 μm, preferably at most 20 μm.

At the in 3 left shown example is the wall 92 the opening 9 essentially vertical. According to another embodiment, the opening may 9 also from the surface 50 the coating to the glass or glass ceramic substrate 2 constrict. An embodiment of this is the in 3 on the right side shown opening 9 , Such an embodiment may be beneficial to opening even in thicker coatings 5 with multiple or stepwise ablation. Preferably, the angle 93 the wall 92 the opening 9 to the vertical of the substrate surface but less than 20 °, preferably less than 15 °. This angle is the mean angle of the wall. This can be easily determined by the ratio of the width 91 the opening on the substrate and the width 95 on the surface of the coating 5 , as well as the thickness of the coating 5 trigonometrically determined become. Accordingly, the thickness D of the coating applies 5 and the difference B of the widths 95 . 91 according to this embodiment: B / 2D ≤ tan (20 °), preferably B / 2D ≤ tan (15 °).

In the preferred layer thicknesses and the maximum width according to the invention 91 According to another embodiment, the opening on the substrate is generally also satisfied with the condition that the width 91 the opening 9 is smaller than the layer thickness of the opaque coating 5 ,

Both the smaller in relation to the layer thickness width of the opening, as well as the possibly low angle of the wall 92 to the vertical cause that already slightly oblique viewing of the opening 9 the line of sight is not through the opening 9 goes, but on the wall 92 ends. This in conjunction with the small width 91 the opening results in the opening remaining invisible to a viewer. This can only be perceived when light from a light source differs from that for the viewer due to the light-blocking coating 5 hidden side of the glass or glass ceramic article 1 through the opening.

However, laser ablation may cause dark discoloration of the coating. If the coating itself is dark, such a discoloration and thus also the opening remain 9 invisible. This is different, however, for coatings with a light shade. Here can be the dark discoloration at the edges of the opening 9 visibly mark. This can be counteracted by adjusting the pulse rate of the laser and the speed with which the laser beam is passed over the coating so that the points of impact of the laser pulses do not overlap, resulting in the desired dot matrix. According to this embodiment of the invention, it is thus also possible to produce for a viewer invisible openings on an opaque coating whose color has an L value in the L * a * b color space of at least 20, preferably of at least 40, more preferably of at least 50 has. The L value of the color of the opaque coating can be determined, for example, with a spectrophotometer. The value refers to an exposed surface of the coating 5 So not on a measured through the glass or the glass ceramic color value.

In order to minimize the thermal influence in the edge region of the opening to be generated and thus avoid the effect of darkening, according to a development of the invention, a top hat profile of the laser beam 7 used. This eliminates the edge areas of the initially Gaussian beam, which have too little energy to ablate the paint, but still have enough energy to heat the coating to discolor it. Another advantage of a TopHat profile is the better contour sharpness, since with a Gaussian profile multi-layer systems are not removed sharp, even if this effect causes blurs in the micrometer range, which are almost or not visible to the eye.

Particularly preferably, the invention is used so that the coating on the side facing away from the user 20 of the glass or glass ceramic substrate 2 is applied. The light of a light source thus first passes through the coating through the opening 9 , then the glass or glass ceramic substrate and then exits from the opposite side 21 out.

The invention can be used in a variety of ways for backlit glass or glass ceramic articles of household appliances. The invention is particularly suitable for hobs. Also, a control panel, such as a stove or oven with a glass or glass ceramic article according to the invention can be realized. The opaque coating is used in the household appliance on the one hand to produce a certain visual appearance, on the other hand to hide the components of the household appliance.

In general, without being limited to the exemplary embodiments described below, the invention also relates to a household appliance with an operating surface which is formed by the glass or glass ceramic article according to the invention, wherein at least one luminous element is arranged in the interior of the domestic appliance, so that light emitted by this luminous element is located the openings 9 of the area 10 in the opaque coating 5 falls and the openings 9 and the substrate 2 can cross.

4 shows an example of a preferred embodiment of such a household appliance 3 in the form of a glass ceramic hob 30 in which the cooking plate by a glass ceramic article according to the invention 1 is formed.

The opaque coating 5 is independent of the type of household appliance 3 preferably on the inside forming side 20 of the glass or glass ceramic substrate 2 applied. In the example of the glass ceramic hob 30 is the opaque coating 5 accordingly on the bottom of the Substrate, here accordingly a glass ceramic substrate 2 , Under the glass ceramic substrate 2 are one or more heating elements 23 arranged to be on the hotplate, respectively on the side 21 to heat up food or cooking utensils. For example, it may be at the one or more heating elements 23 to act induction coils for an induction cooker.

Without limitation to the illustrated embodiment is as a luminous element 18 a light emitting diode used. Depending on the configuration of the opening, an arrangement may also include a plurality of light-emitting diodes 18 be used. The latter is useful, for example, if the openings 9 are very elongated and should be illuminated as evenly as possible. In order to get a lot of light through the small opening, according to another embodiment of the invention, it is also possible to use a laser diode as a luminous element.

In general, without limitation to the illustrated example, it may further be beneficial if a scattering element 19 in front of the light element 18 is arranged. The scattering element 19 extends along a trench-shaped opening 9 and ensures that the light of the lighting element 18 more uniform along the trench-shaped opening 9 is distributed. This results in a more uniform illumination of the with such a trench-shaped opening 9 reached achieved linear display element.

The indicator, which through the illuminated opening 9 is created, for example, may be a cooking zone marker. Such a mark indicates which of the cooking zones is currently active and is being heated. For example, the trench-shaped opening can do this 9 annular around the heating element 23 extend heated area around.

In addition to a scattering element 19 is also a side-emitting light guide for distribution of the luminous element 18 emitted light along the opening 9 suitable. 5 shows an example. The opening 9 is in turn trench-shaped, so that when the illumination of the opening 9 the impression of a linear display element arises. Along the opening 9 extends a side emitting light guide 25 , This is with the light element 18 optically coupled, so that the light of the luminous element 18 in the light guide 25 is coupled. The light guide 25 gives the coupled light distributed along its longitudinal direction and thus distributed along the trench-shaped opening 9 again, leaving the opening 9 is evenly lit. For this embodiment, in addition to a light-emitting diode as a light-emitting element and a laser diode is suitable. With such a laser diode, a high light intensity can also be coupled into a thin light guide. This can be arranged correspondingly close to the opening, so that the light can be efficiently directed to the opening. Regardless of the type of light source, the embodiment with a side emitting fiber is also suitable for guiding light into areas which are strongly heated during operation of the household appliance, since the lighting element itself does not have to be arranged in the heated area. In this way it is possible, inter alia, to create luminous display elements within a cooking zone.

In general, a coating on a glass or glass-ceramic substrate not only serves to prevent the transmission. In addition, a coating may also be advantageous to seal the coated side of the substrate. In the area of the opening 9 However, such a seal would be interrupted. If a translucent sealing layer is used, according to one embodiment of the invention, this can also be done after inserting the opening 9 be applied and cover or close the opening. The light of the luminous element can through the transparent seal the opening 9 continue to happen.

Such a development of the invention, wherein the opening 9 with a transparent sealing layer 6 is closed, shows 6 , The seal can be the opening 9 Cover and / or, as shown, also fill up. As a sealing layer 6 For example, transparent silicone layer (s), silicone-based layer (s) or transparent sol-gel layer (s) are suitable. Furthermore, it is also possible with such a seal a scattering element 18 or to fix a side-emitting light guide or the light-emitting element in the region of the opening.

Under a sealing layer, like the layer 6 represents a coating, which is the glass or glass ceramic material and / or the opaque coating 5 protects against environmental influences. These environmental influences can be, for example, condensation products. So the seal should be a total of dense, for example, compared to liquid and oil-containing substances, such as those found in food. Penetrate such substances into the coating 5 There may be visible, unsightly changes in the visual appearance.

Also the opaque coating 5 itself may be a sealant layer to that of the coating 5 to protect the covered surface of the glass or the glass ceramic.

Another application in addition to a not visible in the off state lighting is also the production of an invisible mark that serves as a mark against plagiarism. If one wishes to determine whether a particular glass or glass ceramic article is original, this can then be easily verified by an examination of the article under backlighting. Accordingly, according to one aspect of the invention, the use of a marker in the form of an inventively prepared, preferably linear opening 9 in the opaque coating 5 to mark the origin of the glass or glass ceramic article. LIST OF REFERENCE NUMBERS 1 Glass or glass ceramic articles 2 Flat glass or glass ceramic substrate 3 household appliance 5 opaque coating 7 Pulsed laser beam 9 Openings or holes in 5 10 Perforated area 11 Device for laser ablation 13 control device 15 galvanometer 16 XY table 18 light element 20, 21 Side surface of 2 23 heating element 70 Impact of 7 71 laser 15 galvanometer 20, 21 Side surface of 2 25 Side emitting light guide 30 Ceramic glass hob 70 Impact of 7 91 Width of 9 on the substrate 2 50 Surface of 5 92 Wall of 9 93 Angle of the wall 92 to the vertical of the substrate surface 95 Width of the opening 9 on the surface 50 from 5

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0868960 B1 [0008]
• DE 102015102743 [0009]
• DE 102008031426 A1 [0047]
• DE 102008031428 A1 [0047]
• DE 102012103507 A1 [0050]

Claims (18)

Method for producing a glass or glass ceramic article ( 1 ), comprising the steps of providing a flat glass or glass ceramic substrate ( 2 ) with two opposite side surfaces ( 20 . 21 ) which, in the visible spectral range from 380 nm to 780 nm, has a light transmittance τ _vis of at least 1%, preferably at least 30%, for visible light comprising the glass or glass ceramic substrate ( 2 ) traverses from one side surface to the opposite side surface, wherein - a side surface of the glass or glass-ceramic substrate ( 2 ) with an opaque coating ( 5 ), which has a light transmission τ _vis of at most 5% in the visible spectral range from 380 nm to 780 nm, wherein - a pulsed laser beam is applied to the opaque coating ( 5 ) and by ablation the coating ( 5 ) multiple times at various locations locally to the surface of the glass or glass ceramic article and thus a perforated area forming grid of a plurality of openings in the opaque coating ( 5 ), such that the opaque coating in the region ( 10 ) of the grid becomes partially transparent. Method according to the preceding claim, characterized in that the grid is formed by points which are arranged at a point distance from one another and have a point size. Method according to the preceding claim, characterized in that the dot pitch is less than 200 microns, preferably less than 150 microns, more preferably less than 100 microns. Method according to one of the preceding claims, characterized in that the spot size is smaller than 30 μm, preferably smaller than 20 μm. Method according to one of the preceding claims, characterized in that the area fraction described by the ratio of ablated area and unprocessed area within a perforated, partially transparent area ( 10 ), greater than 0.5%, where the percentage of ablated area is calculated according to the formula (πr ² x 100%) / (a ² ) where r is the radius of a point and a is the distance between two points. Method according to one of the preceding claims, characterized in that a transition region is developed at the edge of the perforated region, in which further points are ablated so that the area fraction is less than 0.5%. A method according to claim 6, characterized in that the surface portion is changed by <2% / mm. Method according to one of the preceding claims, characterized in that the step of perforating is followed by a cleaning step. Method according to the preceding claim, characterized in that the cleaning step takes place by means of an adhesive roller. Method according to one of the two preceding claims, characterized in that after cleaning the perforated area is provided with a transparent coating or a transparent sealing layer. Method according to one of the preceding claims, characterized in that the ablation threshold of the material of the glass or glass ceramic article ( 2 ) above a wavelength of 532 nm, in particular in the infrared spectral range, preferably at a wavelength of 1064 nm, is higher than the ablation threshold of the opaque coating ( 5 ). Method according to one of the preceding claims, characterized in that the opaque coating ( 5 ) is selected such that it comprises a matrix of an oxide network with decorative pigments embedded therein. Method according to one of the preceding claims, characterized in that the opaque coating ( 5 ) is selected such that it has a color with an L value in the L * a * b color space of at least 20, preferably of at least 40, more preferably of at least 50. Glass or glass-ceramic article produced by a method according to one of the preceding claims, comprising a glass or glass-ceramic substrate having two opposite side surfaces ( 20 . 21 ), where - a side surface ( 20 . 21 ) of the glass or glass ceramic substrate ( 2 ) with an opaque coating ( 5 ) which has a light transmittance τ _vis of at most 5% in the visible spectral range from 380 nm to 780 nm, and an area of the opaque coating having a grid of apertures ( 9 ), which allows the passage of onto the surface of the coating ( 5 ) incident light through the coating ( 5 ) and the glass or glass ceramic substrate, so that the region appears partially transparent, wherein the dot pitch of the openings is less than 200 microns, preferably less than 150 microns, more preferably less than 100 microns. Household appliance ( 3 ) with an operating surface, which is formed by the glass or glass ceramic article according to the preceding claim, and wherein at least one luminous element is arranged in the interior of the domestic appliance, so that light emitted by this luminous element emits light onto the opening (FIG. 9 ) in the opaque coating ( 5 ) and the opening ( 9 ) and can traverse the substrate. Household appliance according to the preceding claim, wherein the opaque coating ( 5 ) on the inside forming side ( 20 ) of the glass or glass ceramic article is applied. Domestic appliance according to one of the two preceding claims, characterized by at least one light-emitting diode or laser diode as light-emitting element ( 18 ). Domestic appliance according to one of the three preceding claims, characterized by a diffuser ( 19 ) or a side-emitting light guide for distributing the light from the element ( 18 ) radiated light through the perforated area.

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