A marking process for a clay-based ceramic piece

Abstract

A method for marking a ceramic piece (1) made of clay, comprising a laser marking operation implementing the marking, by means of a laser (2), of a pattern (3) on the raw or bisque-fired ceramic piece (1), followed by a final firing of the ceramic piece (1) after the laser marking operation to obtain the ceramic piece (1) fired and marked with the pattern (3). The invention finds a preferred, but not limiting, application for decorating or personalizing a ceramic piece used in the fields of tableware, kitchenware, or decorative articles. Abstract figure: Figure 1

Description

Title of the invention: Marking method on a clay-based ceramic part. Technical field

[0001] The invention relates to a marking method on a clay-based ceramic piece.

[0002] It relates more particularly to a method comprising a laser marking operation implementing laser marking of a pattern on a clay-based ceramic piece.

[0003] The invention finds a favorite, and not limiting, application for decorating or personalizing a ceramic piece used in the fields of tableware, cooking or decorative articles. Previous technique

[0004] In a known manner, a ceramic part can be marked using a laser, as described for example in document EPI040017 which implements marking by selective laser sintering, and in document US5554335 which implements marking by laser ablation.

[0005] However, and generally in the prior art, laser marking is systematically applied to a fired ceramic piece, that is to say a ceramic piece which has undergone a final firing, classically between 900 and 1400 degrees Celsius, so as to have a finished ceramic piece, ready for use; and it is this fired ceramic piece which is the subject of the laser marking.

[0006] Although these laser marking processes on fired ceramic parts are generally satisfactory, there is a need to improve the fineness of the marking, in other words to have a pattern with fine, sharp lines and possibly also with material effects. Summary of the invention

[0007] To this end, the invention proposes a marking method on a clay-based ceramic piece, comprising a laser marking operation implementing a marking by means of a laser of a pattern on the raw or bisque-fired ceramic piece, followed by a final firing operation of the ceramic piece after the laser marking operation to obtain the fired ceramic piece marked with the pattern.

[0008] Thus, the process consists of applying a laser marking to a ceramic piece that is raw or bisque-fired, in other words, a ceramic piece that has not yet undergone final firing; a raw ceramic piece being a ceramic piece that has not undergone any firing, and a bisque-fired ceramic piece being a ceramic piece that has underwent a pre-firing (also called first non-final firing or half-firing) whose main objective is to dehydrate the bisque-fired ceramic piece and which takes place at a pre-firing temperature lower than the firing temperature that will be carried out later during the final firing operation.

[0009] This process allows for the obtaining of unique finishes of the pattern, not achievable with laser marking on fired ceramic piece, and at the same time compatible with the food contact standards in force.

[0010] Indeed, the baking, which takes place after the laser marking of the pattern, makes it possible to reveal the marking and in particular to obtain rounded, well-defined edges for the lines of the pattern, in other words to round off the edges of the marking previously made by laser; which contributes to obtaining fine and precise markings.

[0011] In a first embodiment, the laser marking operation is performed on the raw or bisque-fired ceramic piece, which is in its raw state, i.e., without a coating layer. Thus, the laser marking is carried out directly on the raw surface of the raw or bisque-fired ceramic piece.

[0012] In a second embodiment, the process includes, before the laser marking operation, a coating operation implementing a coating of the ceramic piece by at least one layer of coating, so that the laser marking operation is implemented on the at least one layer of coating which covers the raw or bisque-fired ceramic piece.

[0013] In this second embodiment, the ceramic part is covered by one or more coating layers, including an outer coating layer and optionally one or more undercoats. Thus, the laser marking is performed on the outer coating layer, and optionally in the undercoat(s), or even, optionally, down to the surface of the ceramic part.

[0014] According to a feature, in which the coating operation implements an enameling step and / or an engobing step, so that at least one coating layer comprises at least one enameling layer and / or at least one engobing layer.

[0015] According to a first embodiment, the laser marking operation includes at least one laser ablation step implementing one or more passes of the laser over a surface so as to remove material from the surface to form an engraving defining the pattern.

[0016] According to one possibility, the laser ablation step is implemented on the surface of the raw or bisque-fired ceramic piece which is in the raw state, in order to form the engraving directly in the raw or bisque-fired ceramic piece.

[0017] According to another possibility, the laser ablation step is implemented on the surface of at least one coating layer in order to form the engraving at least in said at least one coating layer.

[0018] According to one variant, the at least one coating layer comprises a single coating layer, and the laser ablation step is implemented to form the engraving over at least the entire thickness of said single coating layer by exposing the ceramic part under said single coating layer.

[0019] According to another variant, the at least one coating layer comprises at least two superimposed coating layers comprising an outer coating layer and a sub-coating layer, and the laser ablation step is implemented to form the engraving: - over at least the entire thickness of the at least two superimposed coating layers, exposing the ceramic piece beneath said at least two superimposed coating layers; or - over the entire thickness of the outer coating layer by exposing the undercoat beneath said outer coating layer.

[0020] Thus, it is possible to choose which surface will be exposed, either that of the coating underlayer or one of the coating underlayers or that of the ceramic piece, thus allowing the creation of original aesthetic effects, such as variations in shade.

[0021] According to a second embodiment, the laser marking operation includes at least one selective laser sintering step implementing one or more passes of the laser over a surface so as to locally sinter the surface to define the pattern.

[0022] Selective laser sintering involves passing the laser over the surface to locally sinter the surface, thereby changing the surface state. With this method, it is possible to achieve positive marking (i.e., the pattern corresponds to the sintered area and therefore appears in near relief) or negative marking (i.e., the pattern corresponds to the unsintered area and therefore appears in near-recess).

[0023] According to one variant, the selective laser sintering step is implemented on the surface of the raw or bisque-fired ceramic piece which is in the raw state, so as to form the pattern directly on the raw or bisque-fired ceramic piece.

[0024] According to another variant, the selective laser sintering step is implemented on the surface of at least one coating layer in order to form the pattern on at least one coating layer.

[0025] In an advantageous embodiment, the selective laser sintering step is carried out after the laser ablation step and involves one or more passes of the laser in the engraving obtained at the end of the ablation step.

[0026] Thus, in addition to carrying out laser ablation to form an engraving, a localized selective sintering is planned in the engraving, which helps to obtain a precise finish thanks to this double laser treatment.

[0027] In a particular embodiment, the process includes, before the laser marking operation, a coloring operation of the raw or bisque-fired ceramic piece in order to be colored in the mass.

[0028] In an advantageous embodiment, the laser used during the laser marking operation is a pulsed laser.

[0029] Indeed, this pulsed technology is particularly suitable for working on a ceramic piece based on clay, raw or bisque-fired, in terms of the precision and fineness of the marking, whether by ablation or by selective sintering.

[0030] Advantageously, during the laser marking operation, the laser is operated with a power between 20 and 50 watts.

[0031] This laser power is well suited for implementing the process, as it promotes precision without damaging the ceramic material.

[0032] In a particular embodiment, during the laser marking operation, the laser is operated at a wavelength in the infrared range, and for example at 1064 nm.

[0033] According to one possibility, during the laser marking operation, the laser is operated with a power frequency between 20 and 200 kHz.

[0034] According to another possibility, during the laser marking operation, the laser is moved with a speed of movement between 100 and 5000 millimeters per second, and for example between 300 and 3000 millimeters per second.

[0035] This speed of movement promotes the precision of the marking.

[0036] According to one characteristic, the raw or bisque-fired ceramic piece comprises a mass percentage of clay other than kaolin which is less than 10%.

[0037] According to another feature, the final firing of the ceramic piece is carried out at a maximum firing temperature between 900 and 1400 degrees Celsius, and for example between 1000 and 1350 degrees Celsius. Brief description of the drawings

[0038] Other features and advantages of the present invention will become apparent from the following detailed description, along with several non-limiting examples of implementation, made with reference to the accompanying figures in which:

[0039] [Fig.l] is a schematic view of three stages of a marking process implementing laser ablation directly into the raw or bisque-fired ceramic piece, before firing;

[0040] [Fig.2] is a schematic view of four steps of a marking process putting implements a laser ablation in a coating layer exposing the raw or bisque-fired ceramic piece, before firing;

[0041] [Fig.3] is a schematic view of four steps of a marking process implementing laser ablation in an external coating layer exposing a coating sub-layer, before baking;

[0042] [Fig.4] is a schematic view of four steps of a marking process putting implements laser ablation in an external coating layer and in an under-coating layer to expose the raw or bisque-fired ceramic piece, before firing;

[0043] [Fig.5] is a schematic view of three stages of a marking process implementing selective laser sintering to form a quasi-relief pattern directly on the raw or bisque-fired ceramic piece, before firing;

[0044] [Fig.6] is a schematic view of three steps of a marking process implementing selective laser sintering to form a quasi-recessed pattern directly on the raw or bisque-fired ceramic piece, before firing;

[0045] [Fig.7] is a schematic view of four steps of a marking process putting implements selective laser sintering to form a raised pattern on a coating layer, before firing;

[0046] [Fig.8] is a schematic view of five steps of a marking process employing laser ablation to form an engraving in a coating layer exposing the raw or bisque-fired ceramic piece, then selective laser sintering in the engraving, before firing;

[0047] [Fig.9] is a schematic view of two photographs of an example part ceramics that have been subjected to the process of [Fig.2];

[0048] [Fig. 10] is a schematic view of two photographs of an example of a ceramic piece that has been subjected to the process of [Fig.8].

[0049] [Detailed description of several embodiments of the invention]

[0050] The following detailed description relates to several embodiments of the marking process on a ceramic piece 1 based on clay, and more specifically which includes a mass percentage of clay excluding kaolin which is less than 10%.

[0051] These embodiments all have in common that they include: - a laser marking operation involving marking a pattern 3 on the raw or bisque-fired ceramic piece 1 using a laser 2; and - a final firing operation of the ceramic piece 1, carried out after the laser marking operation, to obtain the ceramic piece 1 fired and marked with the pattern 3.

[0052] Thus, the laser marking operation (which can be laser ablation and / or selective laser sintering) is carried out on a ceramic part before final firing, This helps to limit the effects of laser treatment on technical characteristics.

[0053] Indeed, laser ablation on a fired ceramic piece can lead to the appearance of microcracks in that piece. In the case of the process described in this application, this defect is limited by the fact that the ceramic piece is treated by the laser before its final firing. Similarly, if the fired ceramic piece is glazed and / or engobed, the edges of the treated area may be irregular and have small chips, which detracts from the aesthetics of the piece. Performing the laser treatment on a glazed and / or engobed piece before final firing eliminates these defects while obtaining a very fine pattern. In fact, during final firing, the glaze and / or engobed layer fuses, which rounds the edges of the treated area.During the melting of the enamel and / or engobe layer, it does not spread over the treated area, allowing for a very fine marking.

[0054] Similarly, pre-firing laser treatment, in the case of selective laser sintering, allows for the modification or even fusion of components on the treated surface (whether for the raw ceramic, the glaze layer, and / or the engobe layer), thus resulting in different firing behavior. This difference in behavior allows the pattern to appear. In the case of ceramic pastes containing a colorant, this selective laser sintering can generate a reaction in the colorant, which will react differently during firing, thus resulting in a change in color in the laser-treated area.

[0055] During the laser marking operation, the laser 2 used is a pulsed laser which operates under the following conditions: - a power output between 20 and 50 watts; - a wavelength in the infrared range, for example at 1064 nm; - a power frequency between 20 and 200 kHz; - a speed of movement between 100 and 5000 millimeters per second, and for example between 300 and 3000 millimeters per second.

[0056] In the processes of Figures 1 to 4, the laser marking operation includes at least one laser ablation step consisting of a removal of material under the effect of the laser 2 to engrave the pattern 3.

[0057] In the realization of [Fig. 1], the raw or bisque-fired ceramic piece 1 is supplied in an unglazed state (step a)), i.e., without a coating layer, and the laser ablation step is carried out on the surface of the raw or bisque-fired ceramic piece 1, which is in its unglazed state, so as to form an engraving 20 on this surface of the ceramic piece 1 (step b)), and finally the final firing is carried out (step c)) to obtain the ceramic piece 1 fired and marked with the pattern 3 defined by the engraving 20.

[0058] In the realization of [Fig.2], the raw or bisque-fired ceramic piece 1 is supplied in a raw state (step a)), then it is covered by a coating layer 4, which can be an enamel layer or an engobe layer (step b)), then the laser ablation step is carried out on the surface of the coating layer 4 so as to form an engraving 20 on this surface of the coating layer 4 by exposing the ceramic piece 1 under this coating layer 4 (step c)), and finally the final firing is carried out (step d)) to obtain the fired ceramic piece 1, glazed or engobed, and marked with the pattern 3 defined by the engraving 20.

[0059] In the realization of [Fig.3], the raw or bisque-fired ceramic piece 1 is supplied in a raw state (step a)), then it is covered by two superimposed coating layers 41, 42 comprising an outer coating layer 41 and an under-coating layer 42, which can be enameling layers or engobe layers (step b)), then the laser ablation step is carried out on the surface of the outer coating layer 41 so as to form an engraving 20 exposing the under-coating layer 42 (step c)), and finally the final firing is carried out (step d)) to obtain the fired ceramic piece 1, glazed or engobed, and marked with the pattern 3 defined by the engraving 20.

[0060] In the realization of [Fig.4], the raw or bisque-fired ceramic piece 1 is supplied in a raw state (step a)), then it is covered by two superimposed coating layers 41, 42 comprising an outer coating layer 41 and an under-coating layer 42, which can be enameling layers or engobe layers (step b)), then the laser ablation step is carried out on the two coating layers 41, 42 so as to form an engraving 20 exposing the raw or bisque-fired ceramic piece 1 (step c)), and finally the final firing is carried out (step d)) to obtain the fired ceramic piece 1, glazed or engobed, and marked with the pattern 3 defined by the engraving 20.

[0061] In the processes of Figures 5 to 7, the laser marking operation includes at least one selective laser sintering step implementing one or more passes of the laser over a surface so as to locally sinter the surface to define the pattern 3.

[0062] In the production of [Fig. 5] or [Fig. 6], the raw or bisque-fired ceramic piece 1 is supplied in an unfired state (step a)), and the selective laser sintering step is carried out on the surface of this raw or bisque-fired ceramic piece 1 so as to form a sintered part 10 of the ceramic piece 1 on this surface according to the desired pattern (step b)), and finally the final firing is carried out (step c)) to obtain the fired ceramic piece 1 marked with the pattern 3 which is in quasi- relief in the realization of [Fig.5] and which is almost recessed in the realization of [Fig.6]. Indeed, during step b) of [Fig.5] a positive marking is implemented (that is to say that the motif 3 corresponds to the sintered part 10 and therefore the motif 3 appears in almost relief), while during step b) of [Fig.6] a negative marking is implemented (that is to say that the motif 3 corresponds to the unsintered part bordered by the sintered part 10, and therefore the motif 3 appears almost recessed).

[0063] In the realization of [Fig.7], the raw or bisque-fired ceramic piece 1 is supplied in a raw state (step a)), then it is covered with a coating layer 4, which can be an enameling layer or an engobe layer (step b)), then the selective laser sintering step is carried out on the surface of this coating layer 4 so as to form a sintered part 40 of the coating layer 4 on this surface (step c)), and finally the final firing is carried out (step d)) to obtain the fired ceramic piece 1, glazed or engobed, and marked with the motif 3 which is in quasi-relief in the realization of [Fig.7] because during step c) a positive marking is carried out. Although not illustrated, it is of course conceivable to proceed with a negative marking to obtain the ceramic piece 1 fired, glazed or engobed, and marked with the motif 3 which would then be almost recessed.

[0064] In a final embodiment illustrated in [Fig. 8], the laser ablation step and the selective laser sintering step are combined. More specifically, the selective laser sintering step is carried out after the laser ablation step and involves one or more passes of the laser through the etch 20 obtained at the end of the laser ablation step, so as to locally sinter the internal surface of the etch 20 to define the pattern 3.

[0065] In the production of [Fig. 8], the raw or bisque-fired ceramic piece 1 is supplied in an unfired state (step a)), then it is covered with a coating layer 4, which can be a glaze layer or an engobe layer (step b)), then the laser ablation step is carried out on the surface of the coating layer 4 so as to form an engraving 20 on this surface of the coating layer 4, exposing the ceramic piece 1 beneath this coating layer 4 (step c)), then the selective laser sintering step is carried out on the engraving 20 (step d)) so as to form a sintered portion 10 of the ceramic piece 1 (at the bottom of the engraving) and sintered portions 40 of the coating layer 4 (at the edge of the engraving 20), and finally the final firing is carried out (step e)) to obtain the fired, glazed or engobed ceramic piece 1, and marked with pattern 3 defined by engraving 20.

[0066] Figures 9 and 10 are photographs of examples of results that can be obtained with the marking process, it being noted that these examples are given for illustrative purposes only and are not exhaustive of the finishes that can be achieved.

[0067] Figure 9 shows a ceramic piece made with black ceramic. The clay is colored throughout and covered with a coating, in this case a white glaze, thus forming a ceramic piece with a white glaze. Photograph a) shows the ceramic piece after a laser ablation process to reveal an engraving of a logo and text. This laser ablation treatment removes the glaze to expose the black clay body at the level of the engraving. The ceramic piece then undergoes a final firing at high temperature, which vitrifies the glaze, allowing it to round off at the edges of the engraving, as seen in photograph b). It should be noted that the very fine markings "17" and "68" were covered by the glaze during the final firing. The process used for this example in [Fig. 9] corresponds to the process in [Fig. 2].

[0068] Figure 10 shows a ceramic piece made with black ceramicThe ceramic piece is colored throughout and covered with a coating layer, which in this case is a white glaze; for this example, the ceramic and glaze used are identical to those in Example 9. The ceramic piece was also treated by laser ablation to expose the black clay body at the engraving. Furthermore, to prevent the fine markings from being covered during the final firing, a selective laser sintering step is also performed in the engraving area. Photograph a) shows the ceramic piece after laser ablation and selective laser sintering, before the final firing, and no difference in fineness is visible compared to the example in photograph a) of [Fig. 9].The ceramic piece then undergoes the final firing operation at high temperature, which allows the enamel to vitrify, except that this time it is observed that the enamel has vitrified without covering the finest markings, as visible in photograph b). The process implemented for this example in [Fig. 10] corresponds to the process in [Fig. 8].

Claims

Demands

1. A marking method on a clay-based ceramic piece (1), comprising a laser marking operation implementing a marking by means of a laser (2) of a pattern (3) on the raw or bisque-fired ceramic piece (1), followed by a final firing operation of the ceramic piece (1) after the laser marking operation to obtain the fired ceramic piece (1) marked with the pattern (3), in which the laser marking operation comprises: - at least one laser ablation step implementing one or more passes of the laser (2) over a surface so as to remove material from the surface to form an engraving (20) defining the pattern (3); and - at least one selective laser sintering step, carried out after the laser ablation step, and implementing one or more passes of the laser (2) in the engraving (20) obtained at the end of the laser ablation step, so as to locally sinter the internal surface of the engraving (20).

2. Marking method according to claim 1, wherein the laser marking operation is carried out on the raw or bisque-fired ceramic piece (1) which is in a raw state, i.e. without coating layer (4).

3. Marking method according to claim 1, comprising, prior to the laser marking operation, a coating operation implementing a coating of the ceramic part (1) by at least one coating layer (4; 41, 42), so that the laser marking operation is implemented on the at least one coating layer (4; 41, 42) which covers the raw or bisque-fired ceramic part (1).

4. Marking method according to claim 3, wherein the coating operation implements an enameling step and / or an engobing step, so that at least one coating layer (4; 41, 42) comprises at least one enameling layer and / or at least one engobing layer.

5. A marking method according to claim 3 or 4, wherein at least one coating layer (4; 41, 42) comprises a single coating layer (4), and the laser ablation step is implemented to form the engraving (20) over at least the entire thickness of said single coating layer (4) by exposing the ceramic piece (1) under said single coating layer (4).

6. Marking method according to claim 3 or 4, wherein the at least one coating layer (4; 41, 42) comprises at least two superimposed coating layers (41, 42) comprising an outer coating layer (41) and an undercoating layer (42), and the laser ablation step is carried out to form the engraving (20): - over at least the entire thickness of the at least two superimposed coating layers (41, 42) by exposing the ceramic part (1) under said at least two superimposed coating layers (41, 42); or - over the entire thickness of the outer coating layer (41) by exposing the undercoating layer (42) under said outer coating layer (41).

7. Marking method according to any one of the preceding claims, comprising, before the laser marking operation, a coloring operation of the raw or bisque-fired ceramic piece (1) in order to be colored in the mass.

8. A marking method according to any one of the preceding claims, wherein the laser (2) used during the laser marking operation is a pulsed laser.

9. Marking method according to claim 8, wherein, during the laser marking operation, the laser (2) is operated with a power between 20 and 50 watts.

10. A marking method according to claim 8 or 9, wherein, during the laser marking operation, the laser (2) is operated at a wavelength in the infrared range, and for example at 1064

11. 11111. A marking method according to any one of claims 8 to 10, wherein, during the laser marking operation, the laser (2) is operated with a power frequency between 20 and 200 kHz.

12. A marking method according to any one of claims 8 to 11, wherein, during the laser marking operation, the laser (2) is moved with a speed of movement between 100 and 5000 millimeters per second, and for example between 300 and 3000 millimeters per second.

13. A marking method according to any one of the preceding claims, wherein the raw or bisque-fired ceramic piece (1) comprises a mass percentage of clay other than kaolin which is less than 10%.

14. A marking method according to any one of the preceding claims, wherein the final firing operation of the ceramic piece (1) is carried out at a maximum firing temperature which is between 900 and 1400 degrees Celsius, and for example between 1000 and 1350 degrees Celsius.

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