Method for manufacturing luminous needles by replicating microstructures

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 needles manufactured according to this method.

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

[0004] Patent documents 1 and 2 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 that is excited by a remote primary light source such as an LED.

[0005] Patent document 2 describes, inter alia, a manufacturing method based on the deposition of different resins on pre-cut sheet metal. This method is difficult to implement due to the difficulty in retaining the liquid resin in the openings (in this case, the pre-cut parts of the metal sheet). Furthermore, the use of a sacrificial film to close the openings around the needles is particularly delicate. In addition, this method requires that the attachment part at the tip of the needle be cut beyond the resin that forms the light guide, so that light can be extracted all around the needle. Therefore, the attachment part 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] The object of the present invention is to develop an industrially applicable method for producing luminous needles.

[0008] To this end, the invention relates to a method for producing luminous watch hands 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 explanation 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] 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. [Figure 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. [Figure 3] It concerns the manufacturing of the strip-shaped light guide, the integral manufacturing of the needle body, and the joining of the needle body during the third group of assembly operations. [Figure 4] It concerns the manufacturing of the strip-shaped light guide, the integral manufacturing of the needle body, and the joining of the needle body during the third group of assembly operations. [Figure 5] It concerns the manufacture of strip-shaped light guides, the manufacture of strip-shaped needle bodies, and the joining of the needle bodies 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 INVENTION

[0014] The method according to the invention is intended to manufacture clock hands, in particular watch hands, the edges of which are illuminated by optically coupling light into a light guide, so that the hands can be illuminated.

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

[0016] Specifically, the present invention uses the techniques described in US Pat. No. 6,223,999, 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 this 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 transfer substrates.

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

[0022] Specifically, but without limitation, the light guide comprises a thin, as non-diffusing as possible, 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 onto 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 to assemble the plastic substrate and 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] The first group of operations 1000 relates to the manufacture of light guides, i.e., either the manufacture of integral light guides 30 or the manufacture of light guide strips 35.

[0028] In either case, the first operation 100 is to create a master 1, which is a positive model of the micro-relief to be transferred to the light guide. In particular, but not exclusively, this master 1 is made from a material such as PMMA 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. The relief of the coupling and light extraction microstructures is provided on this master 1 and is then reproduced during the replication process. That is, different microstructures are created, some intended for light coupling / extraction and others as alignment marks for subsequent manufacturing steps.

[0029] The second operation 200 consists in creating a negative tool 2, such as a stamp, based on the master 1 for printing the microstructures. This negative tool 2 may be made, in particular, 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, for example, of PET or TAC with a thickness of 50 to 100 micrometers. The replication of the microstructures is achieved by replicating the microstructures provided by this resin onto the master 1 on the plastic substrate 20 under the action of a buffer 2 that allows printing the microstructures into the resin previously deposited on the plastic substrate 20 and subsequently 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 the details of the microstructures to be accurately reproduced. This replication method can be carried out in a monolithic manner, in sheets (plate to plate or roll to plate, depending on the production method), or in strips. The UV embossing method is particularly advantageous due to the mechanical possibilities it offers, in particular the possibility of replicating structures up to 30 micrometers deep. The output of this second operation is a raw light guide 30 in the case of monolithic production, or a light guide strip 35 comprising multiple raw light guides 30 in the case of strip production.

[0030] The third operation 300 involves pre-cutting the lightguide. To enable the lightguide and needle to be joined together, the raw lightguide 30 must be cut at the location where the needle tube will be located. Without this, assembly would be impossible, as the needle tube would prevent contact with the entire needle surface. This cut is made using cutting means 310, including but not limited to a CO2 laser, and this cut must be aligned to the different microstructures present on the raw lightguide 30. Preferably, alignment marks are already pre-located on the master 1 and are reproduced into 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] Parallel to 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 integrated 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 manufacturing, 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 one variant, the strip of needle bodies 55 may be retained until later separation in these processes.

[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 that has an optical index lower than that of the light guide. This adhesive 6 is deposited onto the needle body and / or onto the light guide, typically by a dispensing means 610.

[0034] Figures 1, 3 to 5 show when bonding 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 bonded product then becomes a bonded needle body 68, or a bonded needle body strip 685, respectively. Figure 2 shows when a light guide is bonded. In this figure, the light guide consists of a one-piece light guide 30 which becomes a bonded light guide 38 after the bonding operation 600.

[0035] This bonding 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 relative to 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, robotic handling means 710, such as a robot coupled to optical recognition means, are 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] For strip manufacturing, the third group of operations 3000 may be performed in a similar manner, whether it is a light guide strip 35 and / or a needle body strip 55. Nevertheless, assembly operation 700 requires great care when assembling the light guide strip 35 and needle body strip 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. Specifically, this final cutting operation 800 is performed by laser cutting means, as already mentioned. Specifically, it is performed by cutting with a femto laser, which gives good results for PET, or cutting with a CO2 laser or the like.

[0038] In the case of one-piece manufacture, the light guide may be finally cut to release the hand during this final cutting operation 800. Preferably, the cut is made approximately 0.1 mm wider than the nominal width of the hand to allow light to escape from around the hand 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 throughout multiple openings in the needle, or both. The illumination design is not limited to the entire periphery, but may 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 final notch.

[0040] An alternative method may be implemented, involving similar steps but in a different order. In particular, this method may involve previously cutting the needle into strips. Advantageously, the cut is approximately 0.1 mm narrower than the nominal width of the assembled blank needle 70, in order to allow light to escape from 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 strip form in the form of a light guide strip 35, which may then be cut and 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 (or 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 cutting is performed by laser or stamping.

[0041] In essence, the microstructures are sufficient to utilize light emitted 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 located below the needle head and "exits" the light guide 30 microstructures arranged along the needle's length. Figures 6 and 7 show examples of light-emitting needles. Each light-emitting needle transmits light emitted by three LEDs arranged in a triangular configuration. Here, the light coupling area is related 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 light guide 30 microstructures along the entire length of the needle, with its ends slightly protruding relative to the needle body 50. This ensures light continuity even if some of the multiple light extraction structures are cut or removed depending on the precision 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 which 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 loss. The choice to use a "transparent" material is advantageous, since it is accessible at the desired thickness. In principle, one could consider a colored material (e.g. fluorescent) while remaining transparent. However, it is essential that the refractive indexes of the two materials are as close as possible. The refractive index of the adhesive that assembles 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 guide. It is not necessary to insert any kind of particles into the light guide.

Claims

1. A method for manufacturing luminous clock hands (80), comprising the steps of: The method comprises separately, on the one hand, through a first group of operations (1000), producing at least one light guide (30) or one light guide strip (35) by replicating a microstructure initially made in a master (1), and, on the other hand, through a second group of operations (2000), producing at least one needle body (50) or one needle body strip (55), After the at least one hand body (50) or the one hand body strip (55) is assembled with the at least one light guide (30) or the one light guide strip (35) through a joining operation (600) and an assembling operation (700), the luminous hand (80) is completed through a final cutting operation (800) so that light escapes from around the luminous hand (80) towards the wearer of the watch including the luminous hand (80) by means of microstructures provided for light coupling and extraction; The method wherein during the final cutting operation (800) the luminous hands (80) are each completed and released using a laser cutting means, the cuts in the final cutting operation (800) being approximately 0.1 mm wider than the nominal width of the luminous hands (80).

2. A method for manufacturing luminous clock hands (80), comprising the steps of: The method comprises separately, on the one hand, through a first group of operations (1000), producing at least one light guide (30) or one light guide strip (35) by replicating a microstructure initially made in a master (1), and, on the other hand, through a second group of operations (2000), producing at least one needle body (50) or one needle body strip (55), After the at least one needle body (50) or the one needle body strip (55) is assembled with the at least one light guide (30) or the one light guide strip (35) through a joining operation (600) and an assembling operation (700), the luminous clock hand (80) is completed through a final cutting operation (800); In the first group of operations (1000), the master (1) is produced by etching means (110), which is a positive model of the fine relief to be transferred to the at least one light guide (30) or the one light guide strip (35) during the first operation (100); A method, wherein the micro-relief comprises microstructures, some of which are provided for light coupling and extraction and some of which are provided as alignment marks for other manufacturing steps.

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

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

5. 5. The method of claim 4, wherein the plastic substrate (20) is selected from PET or TAC having a thickness of 50 to 100 micrometers.

6. The method of claim 4 , wherein the replication of the microstructures is performed by UV embossing or hot embossing.

7. After the second operation (200), in a third operation (300), a cutting means (310) or a CO ２ 5. The method of claim 4, wherein a laser is used to pre-cut the raw light guide at the location where the tube of the luminous clock hand (80) is to be placed, aligned with the alignment markings present on the raw light guide.

8. 3. The method of claim 2, wherein the luminous hands (80) are each completed and released using a laser cutting means during the final cutting operation (800), the cuts in the final cutting operation (800) being made approximately 0.1 mm wider than the nominal width of the luminous hands (80) to allow light to escape from around the luminous hands (80) towards the wearer of the watch including the luminous hands (80) by means of the microstructures provided for light coupling and extraction.

9. 3. The method according to claim 1 or 2, wherein the method is implemented for the purpose of manufacturing a circumferentially illuminated needle, in which the microstructure is replicated.

10. 3. The method according to claim 1 or 2, wherein the method is implemented for the purpose of manufacturing a skeleton needle such that the skeleton needle is illuminated over at least a plurality of openings.

11. 3. The method according to claim 1 or 2, wherein the method is implemented with the aim that needles are manufactured so that they are illuminated only on one side or only at the tip of the needle.

Images