WO1990011985A1

WO1990011985A1 - Surface treatment method for ceramic articles

Info

Publication number: WO1990011985A1
Application number: PCT/GB1990/000506
Authority: WO
Inventors: Teruyuki Tsunabuchi; Shunichi Kumaoka
Original assignee: Hatten Limited; Devons, David, Jon
Priority date: 1989-04-04
Filing date: 1990-04-04
Publication date: 1990-10-18
Also published as: AU5336090A; JPH02263780A

Abstract

The surface of an article (1) is heated (2) to a temperature above 800°C and molten silicon is applied to at least part of the surface to form a coating (3) thereon. Subsequent patterning may be produced by photo etching (4) of at least part of the coating (3) and a further ceramic (5) is applied to the patterning. Alternatively, a thin transparent film (7) on at least part of the coating (3), which may have areas of different thickness formed, e.g. by photo etching.

Description

Surface treatment method for ceramic articles

The present invention relates to a surface treatment method for a ceramic article, for example for decorating the surface of a plate, flower vase, ashtray, tableware etc. made of ceramics.

Up to now decoration of a ceramic article has been added by colouring the surface of the article or by drawing figures and designs on the surface. However, as colouration depends on the colour peculiar to the glaze, it is necessary to prepare a large number of glazes, and the range of colours available is poor. In addition, the designs etc. have to be put on by hand. It is therefore not possible to draw extremely intricate designs, nor is it possible to draw absolutely identical designs, and therefore this process does not lend itself to mass production.

An object of the present invention is to provide a surface treatment method for a ceramic article which is simple and which enables the production of all sorts of design shapes and colours, with the possibility of producing designs of only a few microns thickness and of extreme intricacy, and furthermore at mass production levels .

The invention provides a surface treatment method for a ceramic article, characteried in that the surface of the ceramic article is heated to a temperature above 800"C and molten silicon is applied to at least part of the surface to form a coating thereon.

When coating a ceramic article with molten silicon, cracks which might occur in the coating layer on account of the difference of rates of contraction during cooling, are prevented when the surface temperature of the ceramic article is more than 800^*C.

Preferably, patterning is produced by means of photo etching on at least part of the surface of the silicon coating and one or more further ceramics are applied to the part having the patterning. This allows extremely intricate (for example, in units of microns) designs etc. to be drawn.

In a preferred embodiment a thin transparent film is formed on at least part of the surface of the silicon coating. As a result, it is possible to obtain beautiful articles where the reflective light varies subtly and, furthermore, it is possible to vary the colour shading over the surface by varying the thickness of the transparent film by means of photo etching.

An overglaze may be applied and baked on at least part of the surface of the article. The overglaze protects the surface and gives added colouration.

Embodiments of the invention will now be described with reference to the accompanying drawings, wherein:

Figure 1 is a diagrammatic side view of an article being treated by the method according to the invention,

Figure 2 is a diagrammatic side view similar to Figure 1 showing additional method steps in treating the surface,

Figure 3 is a diagrammatic side view similar to Figure 2 showing alternative additional method steps in treating the surface, and

Figure 4 is a side view of a ceramic article decorated by the method in accordance with the invention.

In Figure 1, a base 1 e. g. a ceramic plate, flower vase, ashtray, piece of crockery etc. made by any known process (for example, by sintering), is pre-heated by a heater 2 until its surface temperature is more than 800"C. Molten silicon is then applied to the heated surface by any known means, such as the shower method, spin coat method etc. , and a coating layer 3 is formed having a thickness of the order of several μ to several 100 μ . The most suitable temperature when coating varies somewhat depending on the type, density etc. of the material of the base 1, but it is important to set the temperature within a range in which the ceramic does not break down.

Furthermore, by carrying out masking treatment for a suitable pattern on the surface of coating layer 3 and/or by chemical etching, a coating layer 3 may be produced having the required pattern. The depth of the etching may be selected as required. It is also possible to expose the surface of the base 1 by removing all of coating layer 3 locally. It is also possible to produce a relief type design. Alternatively, in order to form a partial coating, small amounts only of the melted metal and silicon may be dripped on to the required parts and allowed to spread out naturally.

In Figure 2 a resist 4 is painted onto the coating layer 3 of an article as described in relation to Figure 1. An extremely minute (for example, in microns) pattern, design etc. is projected onto this, and, after exposure and developing, chemical etching is carried out. Another ceramic 5 in a powdered or molten state is affixed to this part. An overglaze 6 is applied to the surface of the article (either to part or all the surface) and thereafter it is baked and finished.

In Figure 3 a ceramic article is produced as in Figure 1, and is heated in a furnace. A thin transparent film 7 (of the order of several 100 A - several 1, 000 A ) composed of SiO, TiO-, SnO,, g₂F etc. is formed on the surface of coating layer 3 by any suitable method such as chemical vaporisation or liquid application. As a result, the light reflected by the transparent film 7 has the colours of the rainbow.

The colours produced by the transparent film 7, such as red, blue, green, gold and intermediate colours formed by subtle combinations thereof, depend on the thickness of the film 7. By removing the transparent film 7 in parts by photo etching after it has been formed thickly over the whole surface and by varying its thickness from place to place, it is possible to obtain an article having extremely beautiful colouring. Finally, if necessary, an overglaze 6 is applied and baked, and a decorative ceramic article may be obtained as shown in Fig. 4.

Claims

Claims :

1. A surface treatment method for a ceramic article (1), characterised in that the surface of the ceramic article (1) is heated (2) to a temperature above 800^*C and molten silicon is applied to at least part of the surface to form a coating (3) thereon.

2. A surface treatment method as claimed in claim 1, wherein patterning is produced by means of photo etching on at least part of the surface of the silicon coating (3) and one or more further ceramics (5) are applied to the part having the patterning.

3. A surface treatment method as claimed in claim 1 or 2, wherein a thin transparent film (7) is formed on at least part of the surface of the silicon coating (3).

4. A surface treatment method for decorative ceramic products as claimed in claim 3, wherein the thickness of the transparent film (7) differs from place to place by partial elimination by means of photo etching thereof.

5. A surface treatment method as claimed in any one of the preceding claims, wherein an overglaze (6) is applied and baked on at least part of the surface of the article.