Method for manufacturing luminous needle by duplicating fine structure

Abstract

To provide a method for manufacturing a luminous needle industrially used.SOLUTION: A method for manufacturing a luminous clock needle 80 comprises: separately manufacturing at least one light guide body 30 or one light guide body strip by duplicating a fine structure initially made in a master 1 through first group operations 1000 and manufacturing at least one needle main body 50 or one needle main body strip through second group operations 2000; assembling the at least one needle main body 50 or the one needle main body strip with the at least one light guide body 30 or the one light guide body strip through a bonding operation 600 and an assembly operation 700; and completing a luminous needle 80 through the last cutting operation 800.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing luminous clock hands.

[0002] The present invention also relates to a needle manufactured according to this method.

[0003] The present invention relates to the manufacture of clock hands, in particular luminous hands. [Background technology]

[0004] US Patent No. 5,399,633 and US Patent No. 5,399,633 describe the operating principle of a fluorescently illuminated needle and a method for manufacturing such a needle, the main components of which consist of a sheet metal, a low refractive index layer whose function is to optically isolate the metal surface, an intermediate refractive index layer whose function is to direct the fluorescence towards the edge of the needle, and a deposit of fluorescent pigment excited by a remote primary light source such as, for example, an LED.

[0005] In particular, the patent application WO 2005 / 023363 describes a manufacturing method based on the deposition of different resins on pre-cut sheet metal. This method is difficult to implement, since it is difficult to keep the liquid resin in the opening (in this case the pre-cut part of the metal sheet). Also, the use of a sacrificial film to close the opening around the needle is particularly delicate. In addition, such a method requires that the attachment at the tip of the needle is cut beyond the resin forming the light guide to allow light extraction all around the needle. Thus, the attachment remains visible. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent Application Publication No. 3845974 [Patent Document 2] International Publication No. 2022 / 122199 Summary of the Invention

[0007] An object of the present invention is to develop a method for manufacturing a luminous needle that can be used industrially.

[0008] To this end, the invention relates to a method for producing a luminous watch hand according to claim 1.

[0009] The present invention also relates to needles made according to this method.

[0010] The present invention relates to the field of watch displays, particularly watch hands, and even more particularly luminous hands. [Brief description of the drawings]

[0011] The objects, advantages and features will be better understood from reading the following detailed description and from the accompanying drawings.

[0012] Figures 1 to 5 show diagrammatically the steps of the method according to the present invention in several alternative sequences in which a first group of operations for producing a light guide and a second group of operations for producing a needle body are performed in parallel before a third group of assembly operations, followed by a fourth group of completion operations.

[0013] [Figure 1] It concerns the integral manufacture of the light guide, the integral manufacture of the needle body, and the joining of the needle body during the third group of assembly operations. [Diagram 2] It concerns the integral manufacture of the light guide, the integral manufacture of the needle body, and the joining of the light guide during the third group assembly operation. [Diagram 3] It concerns the manufacture of the strip-like light guide, the integral manufacture of the needle body and the joining of the needle body during the third group of assembly operations. [Figure 4] It concerns the manufacture of the strip-like light guide, the integral manufacture of the needle body and the joining of the needle body during the third group of assembly operations. [Diagram 5] It concerns the manufacture of a strip-shaped light guide, the manufacture of a strip-shaped needle body, and the joining of the needle body during a third group of assembly operations. [Figure 6]6 and 7 show in schematic form and in plan view two examples of light emitting needles made in accordance with the present invention, each associated with a group of three LEDs. [Figure 7] 6 and 7 show in schematic form and in plan view two examples of light emitting needles made in accordance with the present invention, each associated with a group of three LEDs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The method according to the invention is intended to produce a clock hand, in particular a watch hand, whose edge is illuminated by optically coupling light into a light guide so that the hand can be illuminated.

[0015] In particular, the method is intended to allow monolithic assembly of the needle body, in particular the metal needle body, the light guide system, the means for coupling the light into the light guide, and the means for diffusing the light outside the light guide.

[0016] In particular, the present invention makes use of the techniques described in US Pat. No. 5,399,633, which is incorporated herein by reference.

[0017] The method is based on the replication of microstructures.

[0018] The method according to the invention is based on the assembly, in particular by bonding, of a needle body with a pre-cut light guide, in particular the needle body being superimposed on said light guide.

[0019] The light guide may be in the form of a sheet or strip and may be used as a transport substrate.

[0020] Similarly, strips of needle bodies may also be used as the transfer substrate.

[0021] The needle body may be manufactured in a conventional manner well known to those skilled in the art and is similar to a standard needle.

[0022] In particular, but without limitation, the light guide comprises a thin, possibly non-diffusing, transparent plastic substrate onto which a resin is deposited and structured. The plastic substrate may be made from different materials, for example, but without limitation, PET, TAC, PMMA and PC. PET and TAC offer very good optical / mechanical tradeoffs.

[0023] Methods for depositing and structuring resin on a plastic substrate include selecting a resin with an index close to that of the plastic sheet, and more specifically, but not by way of limitation, the resin is structured by UV embossing to provide bonding areas and light extraction areas.

[0024] The adhesive used in the assembly of the plastic substrate and the needle body must be transparent, non-diffusing, and have an optical index lower than that of the substrate.

[0025] The method comprises the following chronologically distinct operations:

[0026] Parallel operations concern the manufacture of the light guide on the one hand and the needle body on the other hand.

[0027] A first group of operations 1000 relates to the manufacture of a light guide, i.e., either the manufacture of an integral light guide 30 or the manufacture of a light guide strip 35.

[0028] In both cases, a first operation 100 makes a master 1, which is a positive model of the micro-relief to be transferred to the light guide. In particular, but without limitation, this master 1 is made of a material such as PMMA, etc., and is machined using an etching means 110, which may consist of a laser etching means, in particular a CO2 laser, a pico- or femto-laser, a micro-milling means, or a thermal etching means, etc. The relief of the coupling and light extraction microstructures is brought out on this master 1, which is then reproduced during the replication process. That is to say, different microstructures are made, some intended to couple / extract light, and some others as alignment marks for the subsequent manufacturing steps.

[0029] A second operation 200 consists in making a negative tool 2, like a stamp, on the basis of the master 1, for printing the microstructures. This negative tool 2 may in particular be made of nickel or silicone or any suitable material. A plastic substrate 20 is provided, on which a suitable resin is deposited. In particular, but without limitation, the substrate 20 may be made of PET or TAC, for example, with a thickness of 50 to 100 micrometers. The replication of the microstructures is achieved by replicating the microstructures provided by this resin on the master 1 on the plastic substrate 20, under the action of a buffer 2 that allows printing the microstructures in the resin previously deposited on the plastic substrate 20, and then creating at least one raw light guide 30. This replication can be carried out by UV embossing, hot embossing, i.e. hot stamping, or similar methods that allow to accurately reproduce the details of the microstructures. This replication method may be carried out in a monolithic manner, in sheets (plate to plate, roll to plate depending on the manufacturing method) or in strips. The UV embossing method is particularly effective due to the mechanical possibilities it offers, in particular the possibility of replicating structures with a depth of 30 micrometers. The output of this second operation is a green light guide 30, in the case of monolithic production, or a light guide strip 35, which includes a number of green light guides 30, in the case of strip production.

[0030] The third operation 300 concerns the pre-cutting of the lightguide. To be able to join the lightguide and the needle together, the raw lightguide 30 needs to be cut at the location where the needle tube will be placed. Without this, assembly would not be possible, since the needle tube would prevent contact with the entire surface of the needle. This cut is made using a cutting means 310, including but not limited to a CO2 laser. And this cut needs to be aligned to the different microstructures present on the raw lightguide 30. Preferably, alignment marks are already pre-placed on the master 1 and are reproduced on the raw lightguide 30 for this purpose.

[0031] In the case of strip production of light guide strips 35, it is possible to separate each raw light guide by cutting before, during or after this third cutting operation 300.

[0032] In parallel with this first group of operations 1000 relating to the manufacture of light guides, a second group of operations 2000 includes needle body manufacturing operations 400, either in an integral manner for the manufacture of needle bodies 50 or in strip form according to standard methods with final cutting by stamping. In the case of strip manufacture, the needle bodies 50 may be separated immediately after the needle body manufacturing operation 400 in a separation operation 500 using separation means 510 such as stamping means or other suitable cutting means. In a variant, the strips of needle bodies 55 may be retained in these processes until later separation.

[0033] A third group of assembly operations 3000 includes a bonding operation 600 for bonding the raw light guide 30 or light guide strip 35 and / or the needle body 50 or needle body strip 55 prior to assembly of the light guide with the needle body. To this end, an adhesive 6 is selected having an optical index lower than the optical index of the light guide. This adhesive 6 is deposited, typically by a dispensing means 610, on the needle body and / or on the light guide.

[0034] Figures 1, 3 to 5 show where splicing is performed on the needle body. Figures 1 and 3 show a one-piece 50 or Figures 4 and 5 show a needle body strip 55. The spliced ​​product then becomes a spliced ​​needle body 68 or a spliced ​​needle body strip 685 respectively. Figure 2 shows where a light guide is spliced. In this figure the light guide consists of a one-piece light guide 30 which becomes a spliced ​​light guide 38 after the splicing operation 600.

[0035] This joining operation 600 is followed by an assembly operation 700 within the time allowed by the properties of the selected adhesive. During this assembly operation 700, the needle body is optically aligned and placed against the light guide, after which bonding by polymerization proceeds. In particular, but without limitation, a UV optical adhesive is selected due to its rapid polymerization. Advantageously, a robotic handling means 710, such as a robot coupled to an optical recognition means, is used to ensure proper alignment and positioning. At the end of this assembly operation 700, an assembled green needle 70 is obtained, which remains to be finished.

[0036] The third group of operations 3000 may be accomplished in a similar manner for strip manufacture, whether it is light guide strips 35 and / or needle body strips 55. Nevertheless, assembly operation 700 requires careful attention when assembling light guide strips 35 and needle body strips 55.

[0037] The fourth group of operations 4000 includes a final cutting operation 800, the purpose of which is to complete and release each light emitting needle 80. In particular, this final cutting operation 800 is performed by laser cutting means, as already mentioned, in particular by cutting with a femto laser, which gives good results for PET, or by cutting with a CO2 laser or the like.

[0038] In case of one-piece manufacture, the light guide may finally be cut to release the needle during this final cutting operation 800. Preferably, the cut is made approximately 0.1 mm wider than the nominal width of the needle to allow light to escape around the needle towards the watch wearer by means of extraction microstructures provided for this purpose.

[0039] The above method details the manufacture of needles where the needle is illuminated via the periphery of the needle. In the case of skeleton needles, it is possible to have illumination occur over multiple openings in the needle, or both. The illumination design is not limited to the entire periphery, but could be, for example, only on one side of the needle, or only at the tip of the needle, depending on the location of the extractor and the final notch.

[0040] Alternative methods may be implemented that include similar steps but in a different order. In detail, this method may include a pre-cutting of the needle into strips. Advantageously, the cut is approximately 0.1 mm narrower than the nominal width of the assembled raw needle 70, in order to allow light to escape around the needle towards the watch wearer by means of extraction microstructures provided for this purpose. At the same time, the light guide may be manufactured in strips, in the form of light guide strips 35, which may be cut / fixed. During the assembly operation of the needle body and the light guide, an adhesive having an optical index lower than that of the light guide is deposited on the light guide (alternatively on the needle body), typically by dispensing. The light guide is then optically aligned and positioned relative to the needle body, and the adhesive is cured. During a final cutting operation, the needle is finally cut into strips and the assembled needle is released. Advantageously, the cut is made by laser or by stamping.

[0041] In short, the microstructures are sufficient to utilize the light emission coming from an external light source, such as one or more LEDs 90, which "enters" the input light guide 70 of the light emitting needle 80 under the needle head and "exits" the microstructure of the light guide 30 arranged along the length of the needle. Figures 6 and 7 show examples of light emitting needles. Each light emitting needle transmits light emitted by three LEDs arranged in a triangle. Here, the light coupling area relates to the input light guide 70, which is rotationally symmetric as in Figure 6 or point-like as in Figure 7, and the peripheral area is the area of ​​light extraction by the microstructure of the light guide 30 along the entire length of the needle, whose ends protrude slightly relative to the needle body 50. This makes it possible to ensure the continuity of light even if some of the multiple light extraction structures are cut or removed depending on the accuracy of the cutting alignment.

[0042] Regarding materials, the light guide is advantageously a combination of a plastic substrate 20 (support) and a resin on which different microstructures are printed, in particular by a preferred UV embossing method that gives very good results, although hot embossing of the microstructures directly on the substrate 20 may also be considered.

[0043] Both the substrate and the resin must be as transparent as possible to avoid light losses. The choice to use a "transparent" material is advantageous since it is accessible at the desired thickness. In principle, one could also consider a colored material (e.g. fluorescent) while remaining transparent. However, it is essential that the refractive index of the two materials is as close as possible. The refractive index of the adhesive that mounts the light guide to the needle should be as low as possible compared to the refractive index of the substrate in order to optically isolate the light guides. It is not necessary to insert any kind of particles into the light guide.

Claims

1. A method for manufacturing a luminous clock hand (80), comprising the steps of: A method comprising, on the one hand, the production of at least one light guide (30) or one light guide strip (35) by replicating a microstructure initially made on a master (1) through a first group of operations (1000), and, on the other hand, the production of at least one needle body (50) or one needle body strip (55) through a second group of operations (2000), characterized in that said at least one needle body (50) or one needle body strip (55) is assembled with said at least one light guide (30) or one light guide strip (35) through a joining operation (600) and an assembling operation (700), after which said luminous needle (80) is completed through a final cutting operation (800).

2. 2. The method according to claim 1, characterized in that in the first group of operations (1000), the master (1) is produced by an etching means (110) which is a positive model of a micro-relief to be transferred to the at least one light guide (30) or to the one light guide strip (35) during the first operation (100), the micro-relief comprising microstructures, some of which are provided for light coupling and extraction and others of which are provided as alignment marks for other manufacturing steps.

3. 3. The method according to claim 2, characterized in that in the first group of operations (1000), during a second operation (200), a negative tool (2) is made on the basis of the master (1) for printing a microstructure, a substrate (20) made of plastic is provided, a resin is deposited on the substrate (20), and under the action of the negative tool (2) allowing to print the microstructure in the resin previously deposited on the plastic substrate (20) by reproducing the microstructure brought about on the master (1) in the plastic substrate (20) by the resin, a microstructure is replicated in the plastic substrate (20) to produce at least one raw light guide (30) or one light guide strip (35).

4. 4. The method of claim 3, characterized in that the substrate (20) is selected from PET or TAC having a thickness of 50 to 100 micrometers.

5. 4. The method according to claim 3, characterized in that the replication of the microstructures is performed by UV embossing or hot embossing.

6. After the second operation (200), in a third operation (300), a cutting means (310) or a CO ２ 4. The method of claim 3, wherein the raw light guide is pre-cut using a laser at the location where the needle tube is to be placed and aligned to the alignment markings present on the raw light guide.

7. 2. The method according to claim 1, characterized in that during the final cutting operation (800) the luminous hands (80) are each completed and released using laser cutting means, the cut being made approximately 0.1 mm wider than the nominal width of the hand in order to allow the light to escape around the hand towards the wearer of the watch by means of the extraction microstructures provided for this purpose.

8. 2. The method according to claim 1, characterized in that the method is implemented for the purpose of manufacturing a circumferentially illuminated needle, in which the microstructure is replicated.

9. 2. The method of claim 1, wherein the method is implemented for the purpose of manufacturing a skeleton needle such that the needle is illuminated over at least a plurality of apertures.

10. 2. The method according to claim 1, characterized in that the method is implemented for the purpose of manufacturing needles such that they are illuminated only on one side or only at the tip of the needle.

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