Ceramic article with color gradient and method of producing the same

Abstract

To provide a production method capable of mass production of a ceramic part with a color gradient, in particular a bezel of a timepiece, and to provide such a ceramic part.SOLUTION: The present invention produces a ceramic part using uniaxial pressing by a method involving the injection of at least two differently-colored ceramic materials, the ceramic materials being mixed in different weight ratios to create a plurality of mixed materials forming a color gradient.SELECTED DRAWING: Figure 3a

Description

[Technical field]

[0001] The present invention relates to ceramic parts, and more particularly to watch parts such as bezels, made by uniaxial pressing of multiple ceramic materials of different colors that form a continuous change in color to decorate the watch part. [Background technology]

[0002] Ceramic or cermet watch parts are generally obtained by methods involving injection of the material or uniaxial or isostatic pressing of the material followed by sintering. These parts often feature decorations such as indices or numbers on the bezel, which are of a different color than the rest of the part, or simply an overall two-tone decoration (combining two colors). The decorative elements are generally brazed or glued to the sintered blank part. This mechanical assembly between the blank part and the decorative elements can be costly and complicated to implement.

[0003] An alternative to this mechanical assembly is to manufacture blank parts by injecting several materials of different colors, with the color intended to form the decoration after machining. However, manufacturing parts made of ceramics or cermets of different colors is a complex process. In fact, significant shrinkage of up to 30% is observed during sintering. The shrinkage rate depends on several factors, including the choice of material and the amount of material injected. In the bi-injection method or the more common multi-injection method, differential shrinkage occurs during sintering, which can lead to separation at the joints of the various materials.

[0004] To remedy this drawback, US Pat. No. 5,399,633 proposes forming a green body and impregnating a portion of this body with a solution containing a metal that acts as a pigment before sintering. However, a drawback of this method is that it is difficult to obtain a uniform color throughout the entire colored part. Also, Patent Document 2 describes a method for obtaining a ceramic material with a continuous change in color to form a dental prosthesis. However, such a method generally uses isostatic pressing, which is time-consuming and demanding. Moreover, such a method cannot be industrially applied for mass production. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent Application Publication No. 2746243 [Patent Document 2] European Patent Application Publication No. 2965713 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to remedy the above drawbacks by providing a new uniaxial pressing method for obtaining ceramic parts with color gradations. [Means for solving the problem]

[0007] To this end, the present invention relates to a method for producing a ceramic component with a color gradation.

[0008] More specifically, the method of manufacturing a part according to the invention comprises the steps of: providing at least a first ceramic material and a second ceramic material, the first ceramic material being different in color from the second ceramic material; Providing a filling shoe having compartments attached thereto; Preparing a plurality of mixed materials in which the first ceramic material and the second ceramic material are mixed in different weight ratios, while varying the weight ratio to form a desired color gradation; depositing the materials in the compartments of the filling shoe in ascending or descending order according to their weight ratio; preparing an impression in a filling shoe; filling the impression with the mixed material deposited in a filling shoe; removing the filling shoe and uniaxially pressing the mixed material to form a green body; degreasing the green body to obtain the brown body; sintering the brown body to form a blank part; machining the resulting blank part to obtain a ceramic part with a color gradient; Includes.

[0009] The invention also relates to the ceramic parts obtained from this manufacturing method.

[0010] According to another advantageous variant of the invention, The first ceramic material and the second ceramic material include any one of zirconium oxide powder, aluminum oxide powder, titanium nitride powder, silicon nitride powder, titanium carbide powder, chromium carbide powder, tungsten carbide powder, or a mixture of at least two of these powders. The first ceramic material and the second ceramic material each include a different pigment that imparts a different color to the first ceramic material and the second ceramic material. · The pigments are metal oxides or spinels. The pigments are selected from chromium oxide, cobalt oxide, iron oxide, titanium oxide, manganese oxide, molybdenum oxide, cerium oxide, vanadium oxide, zinc oxide, aluminum oxide or mixtures of these oxides. The pigments are cobalt / iron / chromium spinels or cobalt / aluminium spinels. The first ceramic powder and the second ceramic powder each include a binder. The degreasing step consists of thermal degreasing. The sintering step is carried out at a temperature between 1,200°C and 1,800°C for 30 minutes to 20 hours. The sintering step is carried out in an oxidizing or reducing environment.

[0011] The present invention also relates to a ceramic part having a color gradation.

[0012] The part according to the invention comprises several different ceramic materials differing in color and more generally in aesthetic appearance. According to the invention, the decorated part is monolithic and there are no discontinuities between the ceramic materials of the part in order to obtain color gradations. Other characteristics and advantages of the invention will become apparent in the following description of preferred embodiments, given as a non-limiting example with reference to the attached drawings, in which: [Brief description of the drawings]

[0013] [Figure 1] 1 shows a perspective view of a filling shoe used in a manufacturing method according to the invention; [Figure 2a-2b] 1A and 1B show a perspective view and a top view, respectively, of an impression used in a manufacturing method according to the present invention. [Figure 3a] 1 shows an exemplary embodiment of a ceramic part with a continuous change in color obtained using a manufacturing method according to the present invention. [Figure 3b] 1 shows an exemplary embodiment of a ceramic part with a continuous change in color obtained using a manufacturing method according to the present invention. [Figure 4a-4d] 2 illustrates the various steps in a manufacturing method according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention relates to a ceramic part, such as an exterior part or watch part for use in watches and jewellery, which has a colour gradation throughout its entire mass. A "colour gradation" (colour gradient) refers to a continuous change in colour, where at least two colours are used as the basis for creating the continuous change. Of course, the continuous change in colour can have three or more base colours.

[0015] The component according to the invention is made of a ceramic, which may be, for example, zirconium oxide, aluminium oxide, titanium nitride, silicon nitride or a carbide, such as titanium carbide, chromium carbide, tungsten carbide, or a mixture of these ceramics.

[0016] At least one of the ceramic materials includes a pigment that colors the material. The pigment is a metal oxide or spinel selected depending on the color desired. Examples include chromium oxide, cobalt oxide, iron oxide, titanium oxide, manganese oxide, zinc oxide, molybdenum oxide, cerium oxide, vanadium oxide, aluminum oxide, or mixtures of these oxides (e.g., iron oxide / chromium oxide, etc.). For example, for blue, the pigment can be cobalt oxide, for green, the pigment can be chromium oxide, and for brown, the pigment can be iron oxide.

[0017] The part according to the invention can also be a decorative part, such as a component part of a watch, a jewel, a wristlet, etc. In the field of watchmaking technology, the part can be an exterior part, such as a middle, a back, a bezel, a bezel insert, a button, a crown, a wristlet link, a clasp, a buckle, a dial, a hand, a dial index, etc. The part can also be a part of a movement, such as a vibration weight, platinum, etc. By way of example, the part is a bezel 1 made of multiple ceramics of different colors, for example with a gradation from black to turquoise blue. By way of further example, the part can be an acronym of the crown of the watch or an index of the bezel.

[0018] Parts are made by injecting various materials to form a green body and sintering the green body. Although the manufacturing process is illustrated below for a part containing seven successive different colored materials, the part may also be a two, three, four, etc. material part with a different color and / or composition for each successive material injected.

[0019] The method for manufacturing by uniaxial pressing includes the following steps with reference to the figure. · Providing at least a first ceramic material 2 and a second ceramic material 3. The first material differs from the second material by its colour and therefore by its chemical composition. A plurality of mixed materials 20, 21, 22, 23, 24 in which the first ceramic material 2 and the second ceramic material 3 are mixed in different weight ratios are prepared with the weight ratios being varied to form a continuous change in the desired color. Thus, when using two types of ceramic materials, the mixed materials can have weight ratios of 100 / 0, 90 / 10, 80 / 20, 70 / 30, 60 / 40, 50 / 50, 40 / 60, 30 / 70, 20 / 80, 10 / 90, 0 / 100, etc. A person skilled in the art would have no difficulty in using three or more types of ceramic materials, for example, three, four or five types of ceramic materials, to obtain the desired color and the desired color gradation. · Providing a filling shoe 5 that includes compartments arranged to receive the mixture of ceramic materials 20, 21, 22, 23, 24. The number of compartments in the filling shoe 5 depends on the desired final gradation. Place the impression 6 in the filling shoe 5. The mixed material deposited in the compartment of the filling shoe is filled into the impression 6 in ascending or descending order according to the desired weight ratio or gradation. The height of the mixed material deposited in the compartment is at least 0.5 mm and does not exceed the height of the filling shoe. The filling shoe 5 is removed and the mixed material is uniaxially pressed to form a green body 7. ·Degreasing the green body 7 to form the brown body. Sintering the brown body to form a blank part. · Performing a finishing step on the blank part to form part 1.

[0020] Several layers of mixed ceramic materials can be stacked together to form a particular color pattern that is visible from the side of the part.

[0021] The sections of the loading shoe may be linear or non-linear depending on the needs and desired pattern of the practitioner.

[0022] The ceramic material can be a raw material that is primarily ceramic powder or a mixture of ceramic powder and an organic binder.

[0023] When raw materials are used to form the mixed material, a debinding step is necessary before sintering the green body 8. Debinding (debinding) can be done in a solvent to remove materials such as wax, paraffin, etc. Then, thermal debinding can be done at temperatures ranging from 100°C to 800°C.

[0024] The brown body is sintered at a temperature range of 1,200°C to 1,800°C, preferably 1,350°C to 1,450°C, for 30 minutes to 20 hours. Those skilled in the art know that each color has an optimal temperature during sintering and an optimal sintering time so that the color appears quickly after sintering. Therefore, in creating a continuous change, it is particularly useful to select multiple colors with similar sintering temperatures and times, and sinter at an average temperature of the ideal sintering temperatures of the selected multiple colors.

[0025] Preferably, the temperature is increased to the required sintering temperature at a rate of 100° C. to 200° C. per hour. Once sintering is complete, the temperature is gradually decreased at a rate of 100° C. to 200° C. per hour.

[0026] The sintering step is carried out in an oxidizing or reducing environment. For example, sintering can be carried out in an oxygen-containing atmosphere, which can be normal air or an artificially created atmosphere that combines oxygen with other gases. The oxygen-containing atmosphere can be static or have a constant or intermittent flow of gas.

[0027] Depending on the needs of the person skilled in the art, several sintering steps can be performed to achieve the desired result.

[0028] To form the bezel, the blank part is machined to the dimensions of the desired part.

[0029] The method may include a laser ablation process to form decoration on the part. The decoration may consist of, for example, indexes, graduations, or logos.

[0030] After the laser ablation process, the manufacturing method includes finishing steps such as polishing, satin finishing, matte finishing, etc. Also, post-sintering machining can help to make continuous changes in color or specific patterns stand out more clearly depending on the cross-section of the part.

[0031] Typically, the method according to the invention is used to obtain a bezel 1 according to figures 3a and 3b, which has a colour gradient from black to turquoise blue. Naturally, other gradients based on other colours can be obtained using this method.

Claims

1. 1. A method for producing a ceramic part with color gradation by uniaxial pressing, comprising the steps of: - providing at least a first ceramic material (2) and a second ceramic material (3), said first ceramic material (2) being different in color from said second ceramic material (3); - providing a filling shoe (5) fitted with a compartment (4); - preparing a plurality of mixed materials (20, 21, 22, 23, 24) in which the first ceramic material (2) and the second ceramic material (3) are mixed in different weight ratios, while varying the weight ratios to form a desired color gradation; depositing the materials in the compartments of the filling shoe in ascending or descending order according to the weight ratio; - preparing an impression (6) on said filling shoe (5); - filling the impression (6) with the mixed material deposited in the filling shoe (5); - removing the filling shoe and compression molding the mixed material to form a green body (7); - degreasing said green body (7) to obtain a Brownian body; - sintering the brown body to form a blank part; - machining the obtained blank part (8) to obtain a ceramic part (1) with a colour gradation; The method includes:

2. 2. The method according to claim 1, characterized in that the first ceramic material (2) and the second ceramic material (3) comprise any one of zirconium oxide powder, aluminum oxide powder, titanium nitride powder, silicon nitride powder, titanium carbide powder, chromium carbide powder, tungsten carbide powder, or a mixture of at least two of these powders.

3. 2. The method according to claim 1, characterized in that the first ceramic material (2) and the second ceramic material (3) respectively contain different pigments that give the first ceramic material (2) and the second ceramic material (3) different colors.

4. 2. The method of claim 1, wherein the pigment is a metal oxide or a spinel.

5. 5. The method according to claim 4, characterized in that the pigment is selected from chromium oxide, cobalt oxide, iron oxide, titanium oxide, manganese oxide, molybdenum oxide, cerium oxide, vanadium oxide, zinc oxide, aluminum oxide or mixtures of these oxides.

6. 5. The method of claim 4, wherein the pigment is a cobalt / iron / chromium spinel or a cobalt / aluminium spinel.

7. 2. The method of claim 1, wherein the first ceramic powder (2) and the second ceramic powder (3) each comprise a binder.

8. 8. The method of claim 7, wherein the degreasing step comprises thermal degreasing.

9. 2. The method of claim 1, wherein the sintering step is performed at a temperature between 1,200° C. and 1,800° C. for 30 minutes to 20 hours.

10. The method of claim 1 , wherein the sintering step is performed in an oxidizing or reducing environment.

11. A ceramic part, characterized in that it has a color gradation.

12. The part according to claim 11, characterized in that the part is an exterior part or a watch part used in the movement.

13. 12. The part according to claim 11, characterized in that the watch parts used in the exterior part or the movement are selected from the list including: middles, backs, bezels, bezel inserts, buttons, crowns, wristlet links, buckles, dials, hands, dial indexes, oscillating weights and platinum.

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