DE29711916U1 - Glass ceramic articles decorated with ceramic colors - Google Patents

Description

G1125
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07.07.1997

Glass ceramic article decorated with ceramic colours

The subject of the invention is a glass ceramic article decorated with ceramic colors using a screen printing process.

Glass ceramic items have many uses, e.g. as temperature-resistant (fireproof) kitchenware, and especially as cooking surfaces for kitchen stoves.

These items are generally decorated, either for purely aesthetic reasons or to mark the cooking areas on cooking surfaces, for example.
The colors used for these decorations are enamel-based ceramic colors, which are applied using conventional techniques such as screen printing and then fired.

Such measures and glass compositions for decorating, ornamenting and glazing glass ceramics are known, for example, from DE 42 01 286 A1, DE 36 00 109 C2, DE 35 05 922 C1 and DE 34 33 880 C2.

As is known, glass ceramics are produced from a ceramizable glass of a composition as known, for example, from EP 0 220 333 B1, by heat treatment according to a specific temperature-time program (ceramization), whereby temperatures of up to 1000 ^° C can be reached.

Cooking surfaces for hobs, e.g. made of glass ceramic or special gas, are also provided with a decoration made of ceramic colors on their top. On the one hand, this decoration serves to mark the cooking zones and thus to distinguish between cold and hot areas of the cooking surface; on the other hand, the decoration of the cooking surface also fulfills an aesthetic function and enables appliance manufacturers to create independent, distinguishable product lines by adding individual design features.

Until recently, 3 variants of decorating glass-ceramic cooking surfaces using screen printing were possible and available on the market:

1. Single-coloured, monochrome decoration with suitable ceramic colour in the hot and cold areas using decorative structures with a wide range of surface areas or coverage levels.

2. Single-coloured/multi-coloured decoration with suitable ceramic colours only for the functional marking of the cooking surface, in particular the cooking zones

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limitation, but also the residual heat indicator or the company logo, whereby the glass ceramic surface remains largely undecorated in both the hot and cold areas.

3. Multi-coloured decoration with suitable ceramic decorative colours, whereby a gap had to be maintained between the different colours during printing in order to prevent overlaps and intersections of the decorations, which, according to the view at the time, would then lead to the decorative layer flaking off in practical use.

For all cooking surfaces with these decorative variants, signs of wear and fingerprints are often criticized in areas with sparse decoration, which are very noticeable on the largely smooth, shiny surface, especially in exhibition and sales rooms.

In the case of glass ceramic cooking surfaces with only sparse decoration, i.e. only with a cooking zone marking, residual heat indicator and a company logo, in individual cases, particularly when using halogen heaters and with strong radiation from above, as is common in kitchen studio showrooms, the "technology under the cooking surface" may become visible to the viewer or user and disturb their aesthetic sensibilities.

In order to avoid or reduce this undesirable effect, scattered light covers had to be applied. This is a dark layer of paint that is applied to the underside of the cooking surface and which no longer allows visibility.

4. DE 44 26 234 C1 provides a solution to these problems by means of a glass ceramic article decorated with ceramic colors, in particular a glass ceramic cooking surface, wherein on the glass ceramic article, over a first color layer, which covers 1 to 95% of the glass ceramic surface as a basic decoration, at least one further color layer is arranged, which at least partially overlaps the first color layer.

However, even with decoration in accordance with DE 44 26 234 C1, large areas of the surface are still uncovered and, with prolonged use of a cooking surface, signs of wear in the form of scratches, metal abrasion from the pots and sometimes surface changes to the glass ceramic substrate due to unsuitable cleaning agents, which have a noticeable and disturbing effect on the cooking surfaces.

The invention is therefore based on the task of further improving a decorated cooking surface so that the conspicuity of fingerprints, possible signs of wear and scratches is further significantly reduced, whereby the decoration also effectively protects the glass ceramic from surface damage.

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In addition, a bottom coating to cover stray light should be made superfluous here too.

A further object of the invention is to provide a colored glass-ceramic article whose coloring is completely independent of the underlying substrate and whose color of the underlying substrate is no longer recognizable at any point.

This problem has not yet been solved because uniform, full-surface printing does not result in a homogeneous, optically flawless surface, and chipping occurs when the contiguous printing areas are too large.

The objects of the invention are achieved in that at least two grid-shaped structural elements, which correspond to one another and complement one another to form a closed, full-surface decorative covering of the surface of the glass-ceramic article, are applied to the surface of the glass-ceramic article as color applications arranged next to one another.

This creates the impression of full-surface printing and the colour impression of the underlying glass ceramic article is completely eliminated.

Ideally, the grid-shaped structures, which are applied one after the other as color applications in screen printing, lie exactly next to each other, so that the surface of the glass-ceramic article is truly covered with a closed decorative layer.

In practice, however, it can happen that the color applications produced one after the other in screen printing are not ideally arranged next to one another. This means that edge overlaps, overlaps and coverings of the color applications are also possible.

However, this deviation may only be so large that the viewer still has the impression of full-surface printing.

Advantageously, the grid-shaped structural elements are not too coarse, especially smaller than a maximum of 2x2 cm, in order to avoid flaking due to different expansion coefficients of the substrate and the decoration.

In order to minimize this problem of "overprinting" the color applications of the grid-shaped structural elements, it is proposed according to the present invention in a very preferred embodiment that the grid-shaped structural elements that correspond to one another, which are applied as color applications arranged next to one another and which result in the closed, full-surface decorative covering, consist on the one hand of the structural elements themselves (positive) and on the other hand of the spaces between the positive structural elements (negative).

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If, for example, dots are the structural elements (or the screen positive), then the free spaces between the dots are the structural elements (or the screen negative) still necessary for the closed, full-surface decorative covering.

If you first print such a dot grid as a colorful paint application on the substrate, here a dark glass ceramic article, using screen printing, you get colored dots that cover the substrate there.

If this grid-shaped "positive" structural element is reversed phototechnically, so that a negative of the dot grid is created, it is the structural elements corresponding to the dots that now produce the color application in the subsequent screen printing.

If you now use the screen printing process to use the positive of a grid-shaped structural element as one color application and then the precisely fitting negative of the same grid as a second color application, you will create a fully closed decorative print on the surface of the glass ceramic article.

The present invention can basically be applied to all types of grid-shaped structural elements.

The corresponding, grid-shaped structural elements, which are applied as color applications arranged next to one another, can each consist of a different color in terms of their composition and/or their color impression, or each consist of the same color.

Which colors and color combinations are visually advantageous, compatible with each other and suitable for the respective application can be clarified in preliminary tests.

For example, the choice of decorative colors is decisively influenced by the temperature load to which the decorated glass-ceramic article will be exposed during use.

For example, glass ceramic cooktops have completely different requirements for the decorative colors, depending on the type of heat source used: e.g. electric radiant heating, halogen radiators, gas radiant burners, inductive heating, open gas burners and possibly a combination of these.

The full-surface decorative covering of a ceramic hob can be used very advantageously and with comparatively low temperature stress, especially with inductive heating, as the decorated hob is only exposed to the comparatively low temperatures that are returned to the hob by the hot cookware during inductive heating. 280 ⁰ C is unlikely to be reached here.

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It is completely different with electric heating or with gas radiant burners under the glass ceramic cooking surface.

Here, temperature loads of the cooking surface and the decoration of 600 ⁰ C and higher are quite possible.

Some decorative colors are also not compatible with each other, e.g. because they can form certain low-melting compounds when in contact with each other, or because they tend to chip when partially overprinted.

However, full-surface, closed decorative covering according to the invention does not mean that functional areas, such as cooking zones, warming zones, display areas and residual heat displays, and/or lettering, and/or symbols and/or other markings are not defined by windows or openings in the otherwise closed, full-surface decorative covering of the surface of the glass-ceramic article.

For example, it may be advantageous to leave all cooking zones or cooking zones with certain heat sources completely free of any decoration, or, for example, to apply only a grid-shaped structural element as a decorative layer in the area of the cooking zone or a warming zone for reasons of better heat transfer and to dispense with corresponding structural elements in this area.

The invention also provides that in addition to the closed, full-surface decorative covering, further decoration, such as cooking zone rings, can be arranged in the openings.

The invention further provides that a further decorative structure can be arranged over the closed, full-surface decorative covering.

The invention is explained using the embodiments shown in the respective figures and described in more detail below:

Show it:

Figure 1a: An example of a symmetrical grid with the structural element of the "dots" (as positive)

Figure 1b: The grid associated with Figure 1a and also symmetrical with the structural element corresponding to the structural element of the points according to Figure 1a (as a negative)

The structural elements shown in black in Figures 1a and 1b correspond to the color applications printed one after the other and lead to a full-surface and closed decorative covering of the substrate, here a glass ceramic cooking surface.

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Figure 2a: Another example of a symmetrical grid with the structural element of "lines" (as positive)

Figure 2b: The grid belonging to Figure 2a and also symmetrical with the structural element corresponding to the structural element of the lines according to Figure 2a (as a negative).

The structural elements shown in black in Figures 2a and 2b correspond to the color applications printed one after the other and result in a full-surface and closed decorative covering of the substrate, here also a glass ceramic cooking surface.

Figure 3a: An example of a relatively coarse, asymmetrical grid (as a positive)

Figure 3b: The grid belonging to Figure 3a and also asymmetrical with the structural element corresponding to the structural element according to Figure 3a (as a negative).

Figure 4a: Another example of an asymmetrical grid (as positive)

Figure 4b: The grid corresponding to Figure 4a with the structural element corresponding to the structural element according to Figure 4a (as a negative).

The structural elements shown in black in Figures 3a and b and Figures 4a and b correspond to the color applications printed one after the other and then show a closed, full-surface decorative coverage of the substrate.

For this purpose, the first grid-shaped structural element applied to the glass ceramic cooking surface to be decorated using the screen printing process is applied as a paint layer (in the example white) and dried in air or, for example, at 85 ^° C for about 3 minutes.

Then, in addition to this first white grid-shaped structural element, another, second grid-shaped structural element corresponding to the first is printed exactly next to each other using screen printing as a color application (here, for example, black).

The resulting full-surface black and white decorative print is fired during the ceramization of the glass ceramic.

In summary, the advantages of the invention, which makes it possible for the first time to produce a closed, full-surface decorative covering on a glass-ceramic article, should be summarized again:

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Colored glass ceramics can thus be offered without any problem, without having to color the glass itself, which would involve extremely high costs;
The closed decoration, which is distributed over the entire surface of the plate, protects the glass ceramic itself from superficial scratches and signs of wear;
The decor also reduces the visibility of dirt, such as fingerprints;

The undersides of the cooking surfaces no longer need to be coated in order to cover the "technology" underneath;

The decor makes it easier to operate the cooking appliance, for example, by ensuring that the functional areas cannot be confused;
It looks very appealing;

It is easy to produce using conventional methods and ceramic colors.

Claims (5)

-1 - 07.07.1997 RIGHTS TO PROTECTION 1. Glass ceramic articles decorated with ceramic colours using the screen printing process, in particular glass ceramic cooking surfaces, characterized, that on the surface of the glass ceramic article at least two grid-shaped structural elements are applied as color applications arranged next to one another, which correspond to one another and complement one another to form a closed, full-surface decorative covering of the surface of the glass ceramic article. 2. Glass-ceramic article according to claim 1,
characterized, that the grid-shaped structural elements that correspond to one another, which are applied as color applications arranged next to one another and which result in the closed, full-surface decorative covering, consist on the one hand of the structural elements themselves (positive) and on the other hand of the spaces between the positive structural elements (negative). 3. Glass-ceramic articles according to claims 1 and 2,
characterized, that the corresponding grid-shaped structural elements, which are applied as color applications arranged next to one another, each consist of a different color with regard to their composition and/or their color impression. 4. Glass-ceramic articles according to claims 1 and 2,
characterized, that the corresponding grid-shaped structural elements, which are applied as color applications arranged next to one another, each consist of the same color. 5. Glass-ceramic articles according to claims 1 to 4,
characterized, that functional areas such as cooking zones and warming zones, display areas and residual heat indicators and/or lettering, and/or symbols and/or other markings are defined by windows or openings in the otherwise closed, full-surface decorative covering of the surface of the glass-ceramic article.