Method for cutting stack of multiple layers

Abstract

To provide a stack of multiple layers forming a part of a fuel cell, and a method for cutting a stack of at least two layers.SOLUTION: The cutting method comprises: using a laser (40) generating a pulsed beam directed toward a stack (10); piloting the beam so as to follow a pattern to be cut in the stack (10); where the pulse duration of the beam is lower than 10 ps, where the fluence (Φ) of the beam is greater than 127 J / cm2, and where the pulse overlap (θ) of the beam between two successive pulses is greater than 50%.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for cutting a laminate of at least two layers. Such a method can be used, in particular, for cutting a laminate of multiple layers that make up a fuel cell part.

Background Art

[0002] The present invention is particularly situated within the context of the manufacture of fuel cell assemblies. In fact, as shown in FIG. 1, a conventional fuel cell 80 has a laminate of different layers, each having a specific function. Specifically, a conventional fuel cell 80 has, in this order, a negative electrode side separator 81, a negative electrode side gas diffusion layer 82, a negative electrode side catalyst layer 83, a membrane 84, a positive electrode side catalyst layer 85, a positive electrode side diffusion layer 86, and a positive electrode side separator 87.

[0003] The separators 81, 87 have tubes for supplying reagents for the battery reaction and, in some cases, a coolant for the purpose of cooling the fuel cell 80. The separators 81, 87 also aim to conduct the current generated in the fuel cell 80 to an adjacent cell or the terminals of the fuel cell 80.

[0004] The gas diffusion layers 82, 86 are intended to enable the diffusion of the reagents from the separators 81, 87 to the corresponding catalyst layers 83, 85, and the diffusion of the reaction products from the catalyst layers 83, 85 to the corresponding separators 81, 87. For example, such diffusion is made possible by porosity.

[0005] The catalyst layers 83, 85 constitute the electrodes of the positive and negative electrodes, respectively, where the half-reactions that ensure the function of the fuel cell 80 occur. Usually, such catalyst layers 83, 85 are porous to introduce reagents and discharge reaction products. As their names suggest, each catalyst layer 83, 85 contains a catalyst that can function as a catalyst for the corresponding half-reaction of the fuel cell 80.

[0006] The above-mentioned membrane 84 is intended to block electrons generated by the oxidation half-reaction at the negative electrode while allowing the movement of some ions between the positive electrode side catalyst layer 83 and the negative electrode side catalyst layer 85.

[0007] Normally, fuel cells are continuously manufactured on a movable belt production line. A known production line 90 is shown in Figure 2. In such a production line 90, a laminate 91 having a negative electrode side gas diffusion layer 82, a negative electrode side catalyst layer 83, and a membrane 84 is supplied as a continuous belt supported by a support belt. The above laminate 91 passes between two rotating rolls 93a, 93b of a rotary press 93: since the upper roll 93a has a blade 93c having a predetermined shape, the laminate 91 is periodically cut according to the above predetermined shape.

[0008] Thus, in the normal manufacturing method, the laminate is cut thanks to the rotary blade 93c. However, such a rotary blade 93c has the drawbacks of being easily and quickly worn, so that the cutting operation can become inaccurate or incomplete over time. Also, since this blade 93c is an integral part with the roll 93a, every time the shape to be cut is changed, it is necessary to manufacture different specific rolls having a blade 93c corresponding to the desired new shape, which is particularly troublesome and costly. Finally, the use of such blades involves physical contact with fuel cell components and can lead to unwanted contamination.

[0009] Therefore, there is a need for a method for cutting at least a two-layer laminate that can eliminate at least some of the drawbacks of known methods. Summary of the Invention Means for Solving the Problems

[0010] The present invention has been made in view of the above problems.

[0011] The present invention is a method for cutting at least a two-layer laminate, the method comprising: - Using a laser that generates a pulsed beam directed at the laminate, - Directing the beam along a pattern to be cut in the laminate, and The pulse width of the beam is less than 10 ps, The fluence of the beam is greater than 127 J / cm 2 and The overlap of the pulses of the beam between two consecutive pulses is greater than 50%, providing a cutting method.

[0012] In the present disclosure, expressions such as "less than", "greater than", "between", etc. should be interpreted in their broadest sense, i.e., including the case of "the same".

[0013] Thanks to such a laser that generates a pulsed beam directed at the laminate, the laminate can be easily and efficiently cut without using a mechanical blade. Therefore, unlike a mechanical blade that wears out and becomes dull, the accuracy and efficiency of the laser are maintained high and do not decrease over time.

[0014] Also, the laser beam can be directed to cut any desired pattern freely. In this regard, the pattern to be cut can be changed simply by changing the program that directs the laser, without the need to change mechanical parts. As a result, after manufacturing cut-out parts of a predetermined size, it is possible to easily and without delay switch to cut-out parts of other sizes. Therefore, the purchase and storage of multiple mechanical blades are dispensed with, and the usage time of the production line is optimized.

[0015] Furthermore, by using an ultrashort laser pulse, it is possible to cut accurately on the scale of just a few atoms and reduce the risk of damage to the layers along the beam path. In particular, the above parameters make it possible to successfully cut such a two-layer laminate while limiting the occurrence of peripheral damage.

[0016] In some embodiments, the laminate is a membrane electrode assembly having at least a membrane and a catalyst layer laminated to each other. The method according to the present invention is particularly useful in the framework of fuel cell manufacturing.

[0017] In some embodiments, the membrane electrode assembly further has a gas diffusion layer that is cut by a laser beam. It is certainly advantageous to cut as many layers as possible in a single laser operation.

[0018] In some embodiments, the membrane electrode assembly has a first catalyst layer on the first surface side of the membrane and a second catalyst layer on the second surface side of the membrane.

[0019] In some embodiments, the membrane is a proton exchange membrane.

[0020] In some embodiments, the membrane includes a fluoropolymer, optionally a sulfonated tetrafluoroethylene-based fluoropolymer copolymer. In particular, the membrane may be made of commercially available Nafion.

[0021] In some embodiments, the catalyst layer includes platinum and carbon.

[0022] In some embodiments, the gas diffusion layer includes carbon and PTFE. In particular, the gas diffusion layer may be a non-woven carbon paper having microporosity containing PTFE.

[0023] In some embodiments, the thickness of the membrane is greater than 5 μm and optionally greater than 15 μm. However, the thickness of the membrane may be less than 50 μm.

[0024] In some embodiments, the thickness of the catalyst layer is greater than 5 μm and optionally greater than 10 μm. However, the thickness of the catalyst layer may be less than 15 μm.

[0025] In some embodiments, the thickness of the gas diffusion layer is greater than 100 μm, optionally greater than 150 μm, and further optionally greater than 200 μm. However, the thickness of the gas diffusion layer may be less than 250 μm.

[0026] In some embodiments, the pulse width of the beam is less than 8 ps, optionally less than 500 fs, and further optionally less than 350 fs. The smaller the pulse width, the more accurate and cleaner the cutting can be.

[0027] In some embodiments, the spot diameter of the beam is less than 10 μm. The smaller the spot diameter, the more accurate and cleaner the cutting can be.

[0028] In some embodiments, the spot diameter of the beam is greater than 1 μm. With respect to the spot diameter, a compromise must be found between the cutting accuracy and the time required to complete the cutting operation, and such a minimum value is sufficient to ensure an acceptable cutting speed.

[0029] In some embodiments, the wavelength of the beam is between 400 and 1100 nm, optionally between 500 and 580 nm, and further optionally between 515 and 540 nm.

[0030] In some embodiments, the fluence of the beam is greater than 250 J / cm 2 The fluence value can be adjusted according to the number and thickness of the layers to be cut.

[0031] In some embodiments, the fluence of the beam is less than 500 J / cm 2 optionally less than 300 J / cm 2 optionally less than 150 J / cm 2 optionally less than. With respect to the fluence, a compromise must be found between the cutting efficiency, and thus the number of repetitions required to completely cut the laminate, and the degree to which damage to the surroundings during the cutting operation is to be suppressed.

[0032] In some embodiments, the output of the laser is greater than 1 W, optionally greater than 5 W, and further optionally greater than 10 W. However, the output of the laser may be less than 20 W.

[0033] In some embodiments, the pulse frequency of the beam is greater than 50 kHz, optionally greater than 100 kHz.

[0034] In some embodiments, the pulse frequency of the beam is less than 500 kHz, optionally less than 400 kHz.

[0035] In some embodiments, the overlap of the pulses of the beam is greater than 80%, optionally greater than 90%, and further optionally greater than 95%. For the pulse overlap, a compromise must be found between the cutting efficiency and thus the number of repetitions required to completely cut the laminate, and the time required to complete the cutting operation.

[0036] In some embodiments, each part of the pattern to be cut is swept once by the beam of the laser. Thus, the duration of the cutting operation may be quite short.

[0037] In some embodiments, at least a predetermined portion of the pattern to be cut is swept more than once and up to 10 times, optionally 2, 3, or 4 times, by the beam of the laser. Such an option is preferred when the number and / or thickness of the layers is important to ensure that the pattern to be cut is completely cut through the entire thickness of the laminate.

[0038] In some embodiments, during the use of the laser, a support sub-layer is provided under the laminate, and the support sub-layer is not cut by the beam. Such a support sub-layer can improve the cutting efficiency of the laser beam while suppressing peripheral damage. In particular, by using such a support sub-layer, it is possible to cut the same laminate with less fluence, less beam overlap, and / or fewer repetition times, and reduce the duration of the cutting operation and / or peripheral damage.

[0039] In some embodiments, the support sub-layer is composed of an inorganic substance, optionally a metal, ceramic, or glass. These materials can significantly improve the cutting efficiency and are quite resistant to the impact of the laser.

[0040] In some embodiments, the sub-layer is made of an organic material, optionally a polymer material, and in particular, the sub-layer may be made of polyether ether ketone (PEEK). This material is particularly adapted to provide a movable sub-layer used in a roll-to-roll system.

[0041] In some embodiments, the thickness of the support sub-layer is included between 0.1 mm and 50 mm, optionally between 0.5 mm and 10 mm.

[0042] In some embodiments, during the use of the laser, the laminate is clamped by a clamping tool. Such a clamping tool can maintain the laminate in an accurate position relative to the laser and, in particular, reduce local deformation of the laminate, and thus, this helps to improve the accuracy and efficiency of the cutting operation.

[0043] The above features and advantages, and others, will become apparent when reading the following detailed description of exemplary embodiments of the presented method for cutting at least a two-layer laminate. This detailed description refers to the accompanying drawings.

[0044] The features, advantages, and technical and industrial significance of the exemplary embodiments of the present invention will be described below with reference to the accompanying drawings in which like reference numerals represent like elements.

Brief Description of the Drawings

[0045]

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Mode for Carrying Out the Invention

[0046] To make the present invention more specific, exemplary embodiments of a proposed method for cutting a laminate are described in detail below with reference to the accompanying drawings. It should be recalled that the present invention is not limited to these examples.

[0047] Figure 3 shows a membrane electrode assembly 10 intended to be cut. This membrane electrode assembly 10 is a three-layer laminate of a gas diffusion layer 12, a catalyst layer 13, and a membrane 14. In this example, the gas diffusion layer 12 and the catalyst layer 13 are those on the negative electrode side of the fuel cell, but the present invention is of course also applicable to the same layers on the positive electrode side.

[0048] In this example, the gas diffusion layer 12 is a microporous non-woven carbon paper containing PTFE, commercially available under the name SGL Sigracet 22BB, and the thickness of the gas diffusion layer 13 corresponds to 215 μm.

[0049] In this example, the catalyst layer 13 is a layer of platinum and carbon with a platinum content of 46.8% wt, commercially available from Tanaka Kikinzoku Kogyo Co., Ltd., and the thickness of the catalyst layer 13 corresponds to 5 μm.

[0050] In this example, the membrane 14 is a membrane made of Nafion, commercially available under the name NC500, and the thickness of the membrane corresponds to 15 μm.

[0051] The membrane electrode assembly 10 is supported by a sub-layer 20. This sub-layer 20 may be made of different materials such as PEEK, glass, ceramic, etc.

[0052] During the cutting operation, as also shown in FIG. 4, the membrane electrode assembly 10 is clamped within the clamping tool 30 shown in FIG. 5. This clamping tool 30 has a rectangular shape and thus has a clamping base 31 that defines a rectangular central recess 32. The clamping base 31 has shoulders 33 that border the periphery of the central recess 32. Within this central recess 32, a height adjustment insert 34 lying on the shoulders 33 and a sub-layer 20 lying on the height adjustment insert 34 are arranged. On the upper surface 31a of the clamping base 31, a groove 35 surrounding the central recess 32 is provided.

[0053] This clamping tool 30 also has a clamping lid 36 that defines a rectangular central window 37 due to its rectangular shape. On the bottom surface 36a of the clamping lid 36, a seal 38, such as an O-ring type, is provided that surrounds the central window 37 and is arranged to cooperate with the groove 35 when the clamping lid 36 is pressed against the clamping base 31.

[0054] During the cutting operation, the membrane electrode assembly 10 is attached to the upper surface 31a of the clamping base 31 and the sub-layer 20 that is flush with the upper surface 31a. Thereafter, the clamping lid 36 is pressed against the clamping base 31, and the ends of the membrane electrode assembly 10 are clamped between the seal 38 and the groove 35.

[0055] The cutting operation is performed by a laser 40. In this example, the laser 40 is a femtosecond laser of the Trumpf brand. In particular, the laser 40 has a pulse width of 350 fs, a wavelength of 532 nm (green light), and a spot diameter d of 4 μm (the focal plane of the beam). The output P of the laser 40 is adjustable and, in particular, can be adjusted between 5 W and 10 W in this example. The pulse frequency f is also adjustable and, in particular, is between 100 kHz and 400 kHz in this example. Therefore, in this example, the fluence Φ of the laser 40 can be derived from the pulse frequency f and the laser output P and is adjustable between 32 J / cm 2 and 255 J / cm 2 and is adjustable between.

[0056] The beam of the laser 40 is steered by the pilot unit so as to follow the pattern to be cut in the membrane electrode assembly 10. During the cutting operation, the laser beam is steered from one pulse to the other to ensure the overlap of the spots affected by the laser beam. This overlap of the pulses is schematically shown in Fig. 6, where the circle 41 corresponds to the spot of the laser beam during a given pulse, and the circle 42 corresponds to the spot of the laser beam during the pulse immediately following the above given pulse. Accordingly, the hatch area 43 is the area where two consecutive circles 41, 42 overlap, Δx is the pitch between the circles 41, 42 of two consecutive pulses, and thus the overlap θ of the pulses is defined as the ratio of this pitch Δx to the spot diameter d.

[0057] Hereinafter, referring to Figs. 7 to 19, the test results are shown.

[0058] In the first test, corresponding to Figs. 7 and 8, a two-layer laminate having the catalyst layer 13 and the membrane 14 was cut without using a sublayer. The above-described laser 40 was used with different parameters. Specifically, attempts were made to cut 36 squares of 5×5 mm using different parameter sets each time. In this test grid, as shown in detail in the table of Fig. 7, values of three pulse frequencies f, values of two laser outputs P, and values of six pulse overlaps θ were tested. The squares that were cut normally after one repetition of the laser 40 are indicated by thick frames in the table.

[0059] Therefore, it can be seen that all but six of the squares were cut normally. Among the failed tests, numbers 16, 17, and 18 correspond to a fluence Φ of 31.8 J / cm with a pulse overlap θ of less than 70%, and numbers 12, 35, and 36 correspond to a fluence Φ of 63.7 J / cm with a pulse overlap θ of less than 60%. 2 2 2 of the fluence Φ.

[0060] Figure 8 is a photograph of the two-layer laminate after testing. It can be seen that the cutting lines are neat and there is no significant peripheral damage.

[0061] In the second test, corresponding to FIGS. 9 and 10, the gas diffusion layer 12 was cut alone without using the sublayer. The above-described laser 40 was used with different parameters. Specifically, for each square, attempts were made to cut 36 same-grid squares using the same parameter set as above. The squares that were cut normally after two repetitions of the laser 40 are indicated by the thick frames in the table of FIG. 9, and the squares that were cut normally after three repetitions are indicated by the thin frames. There were no squares that were cut normally after one repetition.

[0062] Therefore, it can be seen that only two squares (No. 19 and 20) were cut normally after only two repetitions, and these tests correspond to a fluence Φ of 254.6 J / cm with a pulse overlap θ greater than 90%. 2 Four other squares (No. 1, 2, 7, and 25) were cut normally after three repetitions, and these tests correspond to a fluence Φ of 63.7 J / cm with a pulse overlap θ corresponding to 95%, or a fluence of 127.3 J / cm with a pulse overlap θ greater than 90%. 2 of the fluence Φ, or a fluence of 127.3 J / cm 2 with a pulse overlap θ greater than 90%.

[0063] Figure 10 is a photograph of the gas diffusion layer 12 after testing. It can be seen that the cutting lines are neat and there is no significant peripheral damage.

[0064] In the third test, corresponding to FIGS. 11 to 13, a three-layer laminate having a gas diffusion layer 12, a catalyst layer 13, and a membrane 14 was cut using the sublayer 20. In this third test, this sublayer 20 was made of PEEK, and the thickness of the above sublayer 20 was greater than 100 μm. The above-described laser 40 was used with different parameters. Specifically, attempts were made to cut 20 squares of a new grid. In each column, the same parameters were used, 100 kHz (10 W, thus 254.6 J / cm 2corresponding to a fluence Φ of) or 200 kHz (10 W, thus 127.3 J / cm 2 The values of the pulse frequency corresponding to a fluence Φ of) and the value of the pulse overlap θ of 80 to 95% were tested column by column. The same number of repetitions of the test was performed in each row, and from one row to another, the number of repetitions was increased from 1 to 4 consecutively. The squares that were cut normally are indicated by the thick frames in the table of Figure 11.

[0065] Therefore, it was found that only one square (No. 194) was cut normally, and this test was for a fluence Φ of 254.6 J / cm with a 95% pulse overlap θ after 4 repetitions. 2 corresponds to.

[0066] Figure 12 is a photograph of the laminate after the above test. It can be seen that most of the squares that were not cut normally show damage, and smoke was also visible.

[0067] Figure 13 is a photograph of the above sublayer 20 after another test performed on the same laminate using the test grid of the 36 squares described above. It was found that the above sublayer shows black marks that are signs of wear of the strength and cannot be removed.

[0068] In the fourth test corresponding to Figures 14 to 16, the same three-layer laminate and the same test grid as in the third test were used. However, a different sublayer 20 was used. In fact, in this fourth test, the above sublayer 20 is made of glass, more specifically quartz glass, and has a thickness of 10 mm. The squares that were cut normally are indicated by the thick frames in the table of Figure 14.

[0069] Therefore, it can be seen that using a fluence Φ of 254.6 J / cm with a 95% pulse overlap θ, square No. 191 can be cut normally with only 1 repetition. After 2 repetitions, 2 more squares were cut normally. Square No. 192 has a 90% pulse overlap of 254.6 J / cm 2 and can be cut normally. 2corresponds to the fluence Φ; 252 is 127.3 J / cm with a 95% pulse overlap θ 2 corresponding to the fluence Φ. After repeating 3 times, all the squares were cut normally.

[0070] Figure 15 is a photograph of the laminate after the test. It can be seen that the cutting lines are neat and there is no significant peripheral damage. In particular, the shrinkage of the film 14 with respect to the gas diffusion layer 12 was measured, and its maximum value did not exceed 0.8 mm at the corners of some of the squares.

[0071] Figure 16 is a photograph of the sublayer 20 after another test using the same laminate with the 36 square test grid described above. The scratches were easy to remove, leaving only a low degree of wear.

[0072] In the fifth test corresponding to Figures 17 to 19, the same three-layer laminate and the same test grid as in the third test were used. However, a different sublayer 20 was used. In fact, in this fifth test, the sublayer 20 is made of ceramic, more specifically aluminum oxide (AlO3), and has a thickness of 10 mm. The normally cut squares are indicated by the thick frames in the table of Figure 17.

[0073] Therefore, it can be seen that using a fluence Φ of 254.6 J / cm with a 95% pulse overlap θ, the 191st square can be cut normally in a single repetition. After repeating 2 times, the second square (192nd) corresponding to a fluence Φ of 254.6 J / cm with a 90% pulse overlap θ was also cut successfully. After repeating 3 times, all the squares were cut normally. 2 2 After repeating 3 times, all the squares were cut normally.

[0074] Figure 18 is a photograph of the laminate after the test. It can be seen that the cutting lines are neat and there is no significant peripheral damage. In particular, the shrinkage of the film 14 with respect to the gas diffusion layer 12 was measured, and its maximum value did not exceed 0.2 mm at the ends and 0.4 mm at the corners.

[0075] ​FIG. 19 is a photograph of the sublayer 20 after another test performed using the same laminate with the 36 square test grids described above. It can be seen that the sublayer exhibits black marks. However, these black marks were easily removable and only a low degree of wear remained.

[0076] Although this disclosure refers to specific exemplary embodiments, modifications may be provided to these examples without departing from the general scope of the invention as defined by the claims. In particular, the individual features of different illustrations / embodiments referred to can be combined in additional embodiments. Accordingly, the description and drawings should be considered exemplary rather than restrictive in nature.

Claims

1. A method for cutting a laminate of at least two layers, wherein the method comprises: - using a laser (40) that generates a pulsed beam directed at the laminate (10); - guiding the beam along a pattern to be cut in the laminate (10), wherein the pulse width of the beam is less than 10 ps, The full fluence (Φ) of the beam is greater than 127 J / cm ２ and and the pulse overlap (θ) of the beam between two consecutive pulses is greater than 50%, the cutting method.

2. The method according to claim 1, wherein the laminate (10) is a membrane electrode assembly (10) having at least a membrane (14) laminated to each other and a catalyst layer (13).

3. The method according to claim 2, wherein the membrane electrode assembly (10) further has a gas diffusion layer (12) to be cut by a laser beam.

4. The method according to claim 2 or claim 3, wherein the membrane electrode assembly (10) has a first catalyst layer (13) on a first surface side of the membrane (14) and a second catalyst layer (15) on a second surface side of the membrane (14).

5. The method according to any one of claims 1 to 3, wherein the pulse width of the beam is less than 8 ps, optionally less than 500 fs, and further optionally less than 350 fs.

6. The method according to any one of claims 1 to 3, wherein the spot diameter (d) of the beam is less than 10 μm.

7. The method according to any one of claims 1 to 3, wherein the wavelength of the beam is between 400 and 1100 nm, optionally between 500 and 580 nm, and further optionally between 515 and 540 nm.

8. The fluence (Φ) of the beam is greater than 250 J / cm ２ The method according to any one of claims 1 to 7.

9. The fluence (Φ) of the beam is less than 500 J / cm ２ and optionally less than 300 J / cm ２ and further optionally less than 150 J / cm ２ The method according to any one of claims 1 to 3, wherein the fluence is less than 150 J / cm

10. The method according to any one of claims 1 to 3, wherein the pulse overlap (θ) of the beam is greater than 80%, optionally greater than 90%, and further optionally greater than 95%.

11. The method according to any one of claims 1 to 3, wherein at least a predetermined portion of the pattern to be cut is swept by the beam of the laser (40) more than once and up to 10 times, optionally 2, 3, or 4 times.

12. The method according to any one of claims 1 to 3, wherein a support sublayer (20) is provided under the laminate (10) during use of the laser (40), and the support sublayer (20) is not cut by the beam.

13. The method according to claim 12, wherein the support sub-layer (20) is composed of an inorganic substance, optionally a metal, ceramic, or glass.

14. The method according to claim 13, wherein the thickness of the support sub-layer (20) is between 0.1 mm and 50 mm, optionally between 0.5 mm and 10 mm.

15. The method according to any one of claims 1 to 3, wherein during use of the laser (40), the laminate (10) is clamped by a clamping tool (30).

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