Ceramic component having color gradient and method for manufacturing same

Abstract

The invention relates to a ceramic part, and in particular a bezel (1) of a timepiece, having a color gradient, manufactured by a method of injecting at least two ceramic materials (2, 3) of different colors, said ceramic materials being mixed in different weight ratios to produce a plurality of mixed materials forming the color gradient.

Description

Technical Field

[0001] The present invention relates to a ceramic component, and more particularly to a watch component such as a bezel, which is made by uniaxially pressing ceramic materials of different colors to form a color gradient to decorate the watch component. Background Art

[0002] Ceramic or cermet watch accessories are usually obtained by a process involving injection of material followed by sintering. These accessories are usually decorative, such as hour markers and numbers on the bezel, which are of a different color from the rest of the accessory. The decorative element is usually brazed or bonded to the sintered blank part. This mechanical assembly between the blank part and the decorative element can be costly and complex to implement.

[0003] An alternative to this mechanical assembly is to produce the blank part by injecting a different colored material with the intent to form the decoration after machining. However, the manufacture of ceramic or cermet parts in different colors is a complex process. In fact, a significant shrinkage of up to 30% is observed during sintering. The shrinkage will depend on several factors, including the choice of material and the volume of material injected. In the case of the double-injection or more generally the multi-injection method, differences in shrinkage may occur during sintering, leading to separation of the joints between the different materials or to diffusion of the pigment from one color into another.

[0004] In order to overcome this drawback, document EP 2746243 proposes forming a green body and impregnating a portion of the green body with a solution containing a metal acting as a pigment before sintering. However, the drawback of this method is that it is difficult to obtain a uniform color throughout the colored part.

[0005] Document EP2965713 also describes a method for obtaining ceramic materials with color gradients and forming dentures. However, this method uses isostatic pressing, which is usually time-consuming and demanding. In addition, this method is not industrially applicable to large-scale production. Summary of the invention

[0006] The object of the present invention is to overcome the above-mentioned drawbacks by providing a new uniaxial pressing method for obtaining ceramic parts with a color gradient.

[0007] To this end, the invention relates to a method for producing a ceramic component having a color gradient.

[0008] More specifically, the method for manufacturing a component according to the invention by uniaxial pressing comprises the following steps:

[0009] - preparing at least a first ceramic material and a second ceramic material, the first ceramic material having a different color from the second ceramic material;

[0010] -Preparing a stamping die with an impression;

[0011] - placing a grid within the impression to form compartments within the impression;

[0012] - preparing a plurality of mixed materials, wherein the first ceramic material and the second ceramic material are mixed in different weight ratios, while varying the weight ratios to form a desired color gradient;

[0013] - depositing the materials in the compartments in ascending or descending order according to weight ratio;

[0014] - removing the grid and uniaxially pressing the material to form a green body;

[0015] - defatting the green body to obtain a brown body;

[0016] - Sintering the brown embryo to form a rough component;

[0017] - Finishing of the blank component to obtain the component.

[0018] The invention also relates to a ceramic component obtained by the production method.

[0019] According to other advantageous variants of the invention:

[0020] - Either the first ceramic material or the second ceramic material comprises: 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;

[0021] - the first ceramic material and the second ceramic material each comprise a different pigment which provides the first ceramic material and the second ceramic material with a different color;

[0022] - the pigment is a metal oxide or a spinel;

[0023] - the pigment is chosen from chromium oxide, cobalt oxide, iron oxide, titanium oxide, manganese oxide, molybdenum oxide, cerium oxide, vanadium oxide, zinc oxide, aluminum oxide or a mixture of these oxides;

[0024] - the pigment is cobalt / iron / chromium spinel or cobalt / aluminium spinel;

[0025] - the first ceramic powder and the second ceramic powder each contain a binder;

[0026] - the sintering step is carried out at a temperature between 1,200° C. and 1,800° C. for a time between 30 minutes and 20 hours;

[0027] - The sintering step is carried out in an oxidizing or reducing environment.

[0028] The invention also relates to a ceramic component having a color gradient.

[0029] The component according to the invention comprises a plurality of different ceramic materials, which differ in their colour and, more generally, in their aesthetic appearance. According to the invention, the decorative component is one-piece and has no discontinuities between the ceramic materials of the component, so that a colour gradient is obtained.

[0030] Other characteristics and advantages of the invention will become apparent from the following description of a preferred embodiment presented by way of non-limiting example with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] - Figures 1a to 1c An exemplary embodiment of a ceramic component with a color gradient obtained using the production method according to the invention is shown.

[0032] - Figure 2 A plan view of a blank component with a grid for forming a bezel using the manufacturing method according to the invention is shown.

[0033] - Figures 3a to 3e The various steps in the manufacturing method according to the present invention are shown. DETAILED DESCRIPTION

[0034] The present invention relates to ceramic parts, such as external parts used in watches or jewelry, or even watch accessories, which have a color gradient throughout their entire mass. "Color gradient" means a color gradient with at least two colors used as the basis for creating the gradient. Of course, the color gradient can have more than two base colors.

[0035] The fitting according to the invention is made of ceramic. For example, it can be zirconium oxide, aluminum oxide, titanium nitride, silicon nitride, or even a carbide, such as titanium carbide, chromium carbide or tungsten carbide, or even a mixture of these ceramics.

[0036] By "ceramic material" is meant any type of material known to a person skilled in the art for producing ceramic components, such as powders or granules.

[0037] At least one of the ceramic materials includes a pigment to color the material. The pigment is a metal oxide or spinel selected according to the desired color. 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, such as iron oxide / chromium oxide. For example, for blue, the pigment may be cobalt oxide, for green, the pigment may be chromium oxide, and for brown, the pigment may be iron oxide.

[0038] The component according to the invention may also be a decorative component, such as a component of a watch, jewelry, bracelet, etc. In the field of clocks, the component may be an external component, such as a middle, a back cover, a bezel, a bezel insert, a button, a crown, a bracelet link, a clasp, a clasp, a dial, a pointer, a dial hour marker, etc. It may also be an accessory of a movement, such as a balance wheel, a plate, etc. As an illustration, the component is a bezel 1 made of ceramic of different colors, for example with a gradient from black to turquoise blue. As another example, it may be the initials on the crown, or even the hour markers on the bezel.

[0039] The part is made by uniaxial pressing of various ceramic materials to form a green body. The manufacturing method described below is for a part containing seven consecutive different color materials, but it can also be a part containing 2, 3, 4, etc. materials with different colors, different compositions or even different pigment concentrations.

[0040] Referring to the accompanying drawings, the manufacturing method of uniaxial pressing comprises the following steps:

[0041] - preparing at least a first ceramic powder 2 and a second ceramic powder 3, the first ceramic powder differing from the second ceramic powder by its color and thus by its chemical composition;

[0042] - preparing an impression 5;

[0043] - Placing a grid 6 inside the stamp 5 so as to form compartments 4 inside the stamp, the compartments optionally having various and different forms. In the case of the bezel shown, the compartments may be in the form of sectors, vertical strips or vertical lines. Of course, any other geometric shape is possible, such as waves. The grid is at least 4 mm high and the number of compartments formed depends on the desired final decoration;

[0044] - preparing a plurality of mixed materials 20, 21, 22, 23, 24, wherein the first ceramic material 2 and the second ceramic material 3 are mixed in different weight ratios, while varying the weight ratio from 0 to 100% to form the desired color gradient. Thus, when two ceramic materials are used, the weight ratio of the mixed materials can be 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 will have no difficulty in using more than two ceramic materials, such as three, four or five ceramic materials, to obtain the desired color and the desired color gradient;

[0045] - Depositing the mixed materials 20, 21, 22, 23, 24 in the compartment 4 in ascending or descending order according to the desired weight ratio or gradient. The height of the mixed material deposited in the compartment is at least 0.5 mm and does not exceed the height of the grid;

[0046] - Removing the grid 6 and uniaxially pressing the mixed material to form a green body 7. This is a particularly useful step in terms of achieving good color uniformity throughout the part. In fact, when the grid 6 is removed, the space left by the grid causes the mixed material to settle slightly;

[0047] - hot degreasing green body 7 to obtain brown body;

[0048] - sintering the brown billet to form a green component;

[0049] - Finishing the blank component to form component 1.

[0050] Multiple layers of mixed ceramic materials or powders can be stacked to create specific color patterns visible from the side of the part.

[0051] An example with two powders is given, but one skilled in the art will not find this particularly difficult to prepare.

[0052] The ceramic material used is mainly ceramic powder.

[0053] The green body is thermally debound at a temperature ranging between 100 and 800° C. This step makes it possible to obtain a brown body.

[0054] The brown blank is sintered at a temperature range of 1,200 to 1,800°C, and preferably at a temperature range of 1,350 to 1,450°C for a time between 30 minutes and 20 hours. It is known to those skilled in the art that each color has an optimal temperature and an optimal sintering time during sintering so that the color appears immediately after sintering. Therefore, when producing a gradient, it is particularly useful to select colors with similar sintering temperatures and times and sinter at a temperature that is an average of the desired sintering temperatures of the selected color.

[0055] Preferably, the temperature is raised to the desired sintering temperature at a rate of 100° C. to 200° C. per hour. Once sintering is complete, the temperature is gradually lowered at a rate of 100° C. to 200° C. per hour.

[0056] Depending on the pigment used and the desired color, the brown embryo is sintered in an oxidizing or reducing environment. For example, sintering can be carried out in an oxygen-containing atmosphere, which can be ordinary air or an atmosphere artificially created by combining oxygen and other gases. For reasons of simplicity and cost-effectiveness, ordinary air is preferred. The oxygen-containing atmosphere can be static, or it can be a constant or intermittent airflow.

[0057] As desired by one skilled in the art, multiple sintering steps may be performed to achieve the desired results.

[0058] To form the bezel, the blank component is machined to the dimensions of the desired component.

[0059] The method may include laser ablation processing to form a decoration on the component. The decoration may include, for example, hour markers, graduations or logos.

[0060] After laser ablation processing, manufacturing methods include finishing steps such as polishing, satin finishing, matte finishing, etc. Post-sintering processing can also help to make color gradients or specific patterns more clearly visible, depending on the cross-section of the part.

[0061] Typically, the method according to the invention is used to obtain Figures 1a to 1c The bezel 1 has a color gradient from black to turquoise blue. Of course, other gradient colors based on other colors can be obtained using this method.

Claims

1. A method for producing a ceramic component (1) having a color gradient by uniaxial pressing, the method comprising the following steps: - preparing at least a first ceramic material (2) and a second ceramic material (3), the first ceramic material (2) having a different color from the second ceramic material (3); - preparing an impression (5); - placing a grid (6) inside the stamp (5) to form compartments (4) inside the stamp; - 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 changing the weight ratio to form a desired color gradient; - depositing the materials in the compartments (4) in ascending or descending order according to weight ratio; - removing the grid (6) and uniaxially pressing the material to form a green body (7); - defatting the raw embryo (7) to form a brown embryo; - sintering the brown billet to form a green component; - Mechanically processing the resulting blank component to obtain component (1).

2. The manufacturing method according to claim 1, characterized in that: Any one of the first ceramic material (2) and the second ceramic material (3) comprises: 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. The manufacturing method according to claim 1 or 2, characterized in that: The first ceramic material (2) and the second ceramic material (3) each contain different pigments, and the pigments provide the first ceramic material (2) and the second ceramic material (3) with different colors.

4. The method according to any one of the preceding claims, characterized in that The pigment is a metal oxide or a spinel.

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 a mixture of these oxides.

6. The method according to claim 4, characterized in that The pigment is cobalt / iron / chromium spinel or cobalt / aluminum spinel.

7. The method according to any one of the preceding claims, characterized in that The first ceramic powder (2) and the second ceramic powder (3) each contain a binder, the binder being present in an amount of X wt % to Y wt %.

8. The method according to any one of the preceding claims, characterized in that The sintering step is performed at a temperature between 1,200°C and 1,800°C for a time between 15 minutes and 20 hours.

9. The method according to any one of the preceding claims, characterized in that The sintering step is performed in an oxidizing or reducing environment.

10. A ceramic component (1), characterized in that: It has a color gradient.

11. The component (1) according to claim 10, characterized in that The components are watch accessories used in exterior parts or movements.

12. Component (1) according to claim 10 or 11, characterized in that Said watch accessories for the exterior part or movement are selected from the list consisting of a middle part, a back cover, a bezel, a bezel insert, a push button, a crown, bracelet links, a clasp, a dial, hands, a rod, a rack, dial hour markers, a balance wheel and a bridge.

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