Marking process on a ceramic piece made from clay

Abstract

Method for marking on a ceramic piece (1) based on clay, comprising a laser marking operation implementing a marking by means of a laser (2) of a pattern (3) on the raw or softened ceramic piece (1), followed by a final firing operation 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, and non-limiting, application for decorating or personalizing a ceramic piece used in the fields of tableware, cooking or decorative articles. Abstract figure: Figure 1

Description

Title of the invention: Method for marking a clay-based ceramic part Technical field

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

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

[0003] The invention finds a preferred, and non-limiting, application for decorating or personalizing a ceramic piece used in the fields of tableware, cooking or decorative items. Prior art

[0004] In a known manner, a ceramic part can be marked by means of 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 part, that is to say a ceramic part which has undergone final firing, conventionally between 900 and 1400 degrees Celsius, so as to have a finished ceramic part, ready for use; and it is this fired ceramic part which is the subject of laser marking.

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

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

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

[0009] This process allows the obtaining of singular 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 occurs 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 carried out by laser; which contributes to obtaining fine and precise markings.

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

[0012] In a second embodiment, the method comprises, before the laser marking operation, a covering operation implementing a covering of the ceramic part with at least one coating layer, so that the laser marking operation is implemented on the at least one coating layer which covers the raw or roughened ceramic part.

[0013] In this second embodiment, the ceramic part is covered by one or more coating layers, including an outer coating layer and possibly one or more sub-coating layers. Thus, the laser marking is carried out on the outer coating layer, and possibly in the sub-coating layer(s), or even optionally until reaching the surface of the ceramic part.

[0014] According to one characteristic, the covering operation implements an enameling step and / or an engobing step, such that the 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 comprises 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 roughened ceramic part which is in the raw state, in order to form the etching directly in the raw or roughened ceramic part.

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

[0018] According to a variant, the at least one coating layer comprises a single coating layer, and the laser ablation step is implemented to form the etching 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 an undercoating layer, and the laser ablation step is implemented to form the etching: - over at least the entire thickness of the at least two superimposed coating layers by exposing the ceramic part under said at least two superimposed coating layers; or - over the entire thickness of the outer coating layer by exposing the undercoat layer under 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 making it possible to create original aesthetic effects, such as variations in color.

[0021] According to a second embodiment, the laser marking operation comprises 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, and thus change the surface condition. With this method, it is possible to achieve positive marking (i.e. the pattern corresponds to the sintered part and therefore the pattern appears in quasi-relief) or negative marking (i.e. the pattern corresponds to the unsintered part and therefore the pattern appears in quasi-hollow).

[0023] According to a variant, the selective laser sintering step is implemented on the surface of the raw or roughened ceramic part which is in the raw state, so as to form the pattern directly on the raw or roughened ceramic part.

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

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

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

[0027] In a particular embodiment, the method comprises, before the laser marking operation, an operation of coloring the raw or roughened ceramic part 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 softened, in terms of precision and fineness of marking, whether by ablation or by selective sintering.

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

[0031] This laser power is well suited for implementing the process, because it promotes precision without harming 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 pulse frequency of between 20 and 200 kHz.

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

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

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

[0037] According to another characteristic, the final firing operation of the ceramic part 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. Brief description of the drawings

[0038] Other characteristics and advantages of the present invention will appear on reading the detailed description below, of several non-limiting examples of implementation, made with reference to the appended figures in which:

[0039] [Fig.l] is a schematic view of three stages of a marking process implementing laser ablation directly in the raw or deglazed ceramic part, before firing;

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

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

[0042] [Fig.4] is a schematic view of four steps of a marking process involving implements laser ablation in an outer coating layer and in an undercoating layer to expose the raw or deglazed ceramic part, before firing;

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

[0044] [Fig.6] is a schematic view of three stages of a marking process using selective laser sintering to form a quasi-hollow pattern directly on the raw or roughened ceramic part, before firing;

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

[0046] [Fig.8] is a schematic view of five steps of a marking process using laser ablation to form an etching in a coating layer exposing the raw or roughened ceramic part, then selective laser sintering in the etching, before firing;

[0047] [Fig.9] is a schematic view of two photographs of an example of a part ceramic having undergone the process of [Fig.2];

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

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

[0050] The detailed description which follows relates to several embodiments of the marking method on a ceramic part 1 based on clay, and more precisely which comprises a mass percentage of clay excluding kaolin which is less than 10%.

[0051] These embodiments all have in common the fact that they comprise: - a laser marking operation implementing a marking by means of a laser 2 of a pattern 3 on the ceramic part 1 which is raw or roughened; 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 may be laser ablation and / or selective laser sintering) is carried out on a ceramic part before final firing, which limits the effects of laser treatment on technical characteristics.

[0053] Indeed, laser ablation on a fired ceramic part can cause microcracks to appear in this fired part. In the case of the method described in the present application, this defect is limited by the fact that the ceramic part is treated by the laser before its final firing. Similarly, if the fired ceramic part is glazed and / or engobed, the edges of the treated area may be irregular and have small chips, which deteriorates the aesthetics of the part. Carrying out the laser treatment on a glazed and / or engobed part before the final firing makes it possible to eliminate these defects while obtaining a very fine pattern. Indeed, during the final firing, the glaze layer and / or the engobing layer fuses, which results in the rounding of the edges of the treated area.When melting the enamel layer and / or the engobing layer, it does not spread over the treated area, allowing very fine marking to be obtained.

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

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

[0056] In the methods of Figures 1 to 4, the laser marking operation comprises 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 embodiment of [Fig.l], the raw or softened ceramic part 1 is provided in a raw state (step a)), i.e. without a coating layer, and the laser ablation step is implemented on the surface of the raw or softened ceramic part 1 which is in the raw state so as to form an engraving 20 on this surface of the ceramic part 1 (step b)), and finally the final firing is implemented (step c)) to obtain the ceramic piece 1 fired and marked with the pattern 3 defined by the engraving 20.

[0058] In the embodiment of [Fig.2], the raw or roughened ceramic part 1 is provided in a raw state (step a)), then it is covered by a coating layer 4, which may be an enamel layer or a coating layer (step b)), then the laser ablation step is implemented 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 part 1 under this coating layer 4 (step c)),, and finally the final firing is implemented (step d)) to obtain the fired, enameled or coated ceramic part 1, and marked with the pattern 3 defined by the engraving 20.

[0059] In the embodiment of [Fig. 3], the raw or unfired ceramic part 1 is provided in a raw state (step a)), then it is covered by two superimposed coating layers 41, 42 comprising an outer coating layer 41 and a coating sub-layer 42, which may be enameling layers or engobing 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 coating sub-layer 42 (step c)), and finally the final firing is carried out (step d)) to obtain the fired, enameled or engobed ceramic part 1, and marked with the pattern 3 defined by the engraving 20.

[0060] In the embodiment of [Fig. 4], the raw or deglazed ceramic part 1 is provided in a raw state (step a)), then it is covered by two superimposed coating layers 41, 42 comprising an outer coating layer 41 and a sub-coating layer 42, which may be enamel layers or engobing layers (step b)), then the laser ablation step is implemented on the two coating layers 41, 42 so as to form an engraving 20 exposing the raw or deglazed ceramic part 1 (step c)), and finally the final firing is implemented (step d)) to obtain the fired, enameled or engobed ceramic part 1, and marked with the pattern 3 defined by the engraving 20.

[0061] In the methods of Figures 5 to 7, the laser marking operation comprises 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 embodiment of [Fig.5] or [Fig.6], the raw or softened ceramic part 1 is provided in a raw state (step a)), and the selective laser sintering step is carried out on the surface of this raw or softened ceramic part 1 so as to form a sintered part 10 of the ceramic part 1 on this surface according to the desired pattern (step b)), and finally the final firing is carried out (step c)) to obtain the ceramic part 1 fired and marked with the pattern 3 which is in quasi- relief in the realization of [Fig.5] and which is quasi-hollow in the realization of [Fig.6]. Indeed, during step b) of [Fig.5] a positive marking is implemented (i.e. pattern 3 corresponds to the sintered part 10 and therefore pattern 3 appears in quasi-relief), while during step b) of [Fig.6] a negative marking is implemented (i.e. pattern 3 corresponds to the non-sintered part bordered by the sintered part 10, and therefore pattern 3 appears in quasi-hollow).

[0063] In the production of [Fig. 7], the raw or deglazed ceramic part 1 is provided in a raw state (step a)), then it is covered by a coating layer 4, which may be an enamel layer or a coating layer (step b)), then the selective laser sintering step is implemented 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 implemented (step d)) to obtain the fired, enameled or coated ceramic part 1, and marked with the pattern 3 which is in quasi-relief in the production of [Fig. 7] because during step c) a positive marking is implemented. Although not illustrated, it is of course possible to carry out negative marking to obtain the ceramic piece 1 fired, glazed or engobed, and marked with the motif 3 which would then be almost hollow.

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

[0065] In the embodiment of [Fig.8], the raw or uncured ceramic part 1 is provided in a raw state (step a)), then it is covered by a coating layer 4, which may be an enamel layer or an engobing layer (step b)), then the laser ablation step is implemented on the surface of the coating layer 4 so as to form an etching 20 on this surface of the coating layer 4 by exposing the ceramic part 1 under this coating layer 4 (step c)), then the selective laser sintering step is implemented on the etching 20 (step d)) so as to form a sintered part 10 of the ceramic part 1 (at the bottom of the etching) and sintered parts 40 of the coating layer 4 (at the edge of the etching 20), and finally the final firing is implemented (step e)) to obtain the fired, enameled or uncured ceramic part 1 engobed, 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 of course that these examples are given for illustrative purposes and are not exhaustive of the finishes that can be achieved.

[0067] In [Fig.9] a ceramic piece made with black ceramic is visible tinted in the mass and covered with a coating layer which is here a layer of white enamel, thus forming a ceramic piece enameled with a white enamel. Photograph a) shows the ceramic piece after a laser ablation step in order to reveal an engraving forming a logo and writing. This laser ablation treatment removes the enamel in order to reveal the black colored paste at the level of the engraving. The ceramic piece then undergoes the final firing operation, at high temperature, which allows the enamel to vitrify allowing it to round off on the edges of the engraving, as visible in photograph b). It should be noted that the very fine markings "17" and "68" were covered by the enamel during the final firing. The process implemented for this example in [Fig.9] corresponds to the process in [Fig.2].

[0068] In [Fig. 10] a ceramic piece made with black ceramic is visibletinted in the mass and covered with a coating layer which is here a layer of white enamel; for this example, the ceramic and the enamel used are identical to those of example 9. The ceramic piece has also been treated by laser ablation in order to reveal the black colored paste at the engraving level. In addition, so that the fine markings are not covered during the final firing, a selective laser sintering step is also carried out, in the engraving. Photograph a) shows the ceramic piece after laser ablation and selective laser sintering, before the final firing, and no difference in fineness can be seen 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

Claims

1. Method for marking on a ceramic piece (1) based on clay, comprising a laser marking operation implementing a marking by means of a laser (2) of a pattern (3) on the raw or softened ceramic piece (1), followed by a final firing operation of the ceramic piece (1) after the laser marking operation to obtain the ceramic piece (1) fired and marked with the pattern (3).

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

3. Marking method according to claim 1, comprising, before the laser marking operation, a covering operation implementing a covering 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 softened ceramic part (1).

4. Marking method according to claim 3, wherein the covering operation implements an enameling step and / or an engobing step, so that the 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 any one of claims 1 to 4, wherein 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 in the surface to form an engraving (20) defining the pattern (3).

6. A marking method according to claims 3 and 5, wherein the at least one coating layer (4; 41, 42) comprises a single coating layer (4), and the laser ablation step is carried out to form the etching (20) over at least the entire thickness of said single coating layer (4) by exposing the ceramic part (1) under said single coating layer (4).

7. A marking method according to claims 3 and 5, wherein the at least one coating layer (4; 41, 42) comprises at least at least two superimposed coating layers (41, 42) comprising an outer coating layer (41) and a sub-coating layer (42), and the laser ablation step is carried out to form the etching (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 sub-coating layer (42) under said outer coating layer (41).

8. A marking method according to any one of the preceding claims, wherein the laser marking operation comprises at least one selective laser sintering step implementing one or more passes of the laser (2) over a surface so as to locally sinter the surface to define the pattern (3).

9. Marking method according to claims 5 and 8, in which the selective laser sintering step is carried out after the laser ablation step and implements 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) to define the pattern (3).

10. Marking method according to any one of the preceding claims, comprising, before the laser marking operation, an operation of coloring the raw or softened ceramic part (1) in order to be colored in the mass.

11. A marking method according to any preceding claim, wherein the laser (2) employed during the laser marking operation is a pulsed laser.

12. A marking method according to claim 11, wherein, during the laser marking operation, the laser (2) is operated with a power of between 20 and 50 watts.

13. A marking method according to claim 11 or 12, wherein, during the laser marking operation, the laser (2) is operated at a wavelength in the infrared range, and for example at 1064 nm.

14. A marking method according to any one of claims 11 to 13, wherein, during the laser marking operation, the laser (2) is operated with a pulse frequency of between 20 and 200 kHz.

15. A marking method according to any one of claims 11 to 14, wherein, during the laser marking operation, the laser (2) is moved with a displacement speed of between 100 and 5000 millimeters per second, and for example between 300 and 3000 millimeters per second.

16. Marking method according to any one of the preceding claims, in which the raw or hardened ceramic part (1) comprises a mass percentage of clay excluding kaolin which is less than 10%.

17. Marking method according to any one of the preceding claims, in which the final firing operation of the ceramic part (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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