METHOD FOR FORMING A SHEET-LIKE SUBSTRATE

Abstract

The invention relates to a method for forming a dimensionally stable three-dimensional shape into a sheet-like substrate (3) of thermoplastic material comprising the steps of: a.) providing a mould including a first die (1) with a first template surface (11) for contacting an upper surface (31) of the substrate (3) and a second die (2) with a second template surface (21) for contacting a lower surface (32) of the substrate (3) opposite the upper surface (31) of the substrate (3); each template surface (11, 21) having an inverse of a desired shape to be transformed to the upper and lower surfaces (31, 32) of the substrate (3); and at least one of the first die (1) and the second die (2) being transparent to electromagnetic waves of a predetermined wavelength; b.) providing at least one absorption layer (5, 5) being able to be heated by absorption of an electromagnetic irradiation (4, 4) of the predetermined wavelength and thereby heating the thermoplastic substrate (3) to or above its glass transition temperature; c.) placing the substrate (3) between the first and the second die (1, 2) of the mould and closing the mould; d.) irradiating the absorption layer (5, 5) with the electromagnetic irradiation (4, 4) in order to heat the thermoplastic substrate (3) to or above its glass transition temperature during a sufficient time to transform the thermoplastic substrate into the three-dimensional shape.

Claims

1-11. (canceled)

12. A method for forming a dimensionally stable three-dimensional shape into a sheet-like substrate of a thermoplastic material, the method comprising: providing a mould including a first die with a first template surface for contacting an upper surface of the substrate and a second die with a second template surface for contacting a lower surface of the substrate opposite the upper surface of the substrate; each template surface having an inverse of a desired shape to be transformed to the upper and lower surfaces of the substrate; and at least one of the first die and the second die being transparent to electromagnetic waves of a predetermined wavelength; providing at least one absorption layer being able to be heated by absorption of an electromagnetic irradiation of the predetermined wavelength and thereby heating the thermoplastic substrate to or above a glass transition temperature of the thermoplastic substrate; placing the substrate between the first and the second die of the mould and closing the mould; irradiating the absorption layer with the electromagnetic irradiation to heat the thermoplastic substrate to or above the glass transition temperature during a sufficient time to transform the thermoplastic substrate into the three-dimensional shape.

13. The method according to claim 12, wherein at least one of the first template surface and the second template surface is provided with the absorption layer.

14. The method according to claim 12, wherein the sheet-like substrate is provided with the absorption layer.

15. The method according to claim 12, wherein the sheet-like substrate comprises a material suitable to absorb the electromagnetic irradiation of the predetermined wavelength and forms the absorption layer in order to be heated to or above the glass transition temperature.

16. The method according to claim 12, wherein the sheet-like substrate comprises at least two parts.

17. The method according to claim 16, wherein the at least two parts are melted together during the step of irradiating the absorption layer.

18. The method according to claim 12, wherein the absorption layer is provided only to regions where the sheet-like substrate is to be melted.

19. The method according to claim 12, wherein the surface of the sheet-like substrate is provided with a hydrophobic coating prior to placing the substrate between the first and second die.

20. A device for forming a dimensionally stable three-dimensional shape into a sheet-like substrate of thermoplastic material, the device comprising: a mould including a first die with a first template surface for contacting an upper surface of the substrate and a second die with a second template surface for contacting a lower surface of the substrate opposite the upper surface of the substrate, each template surface having an inverse of a desired shape to be transformed to the upper and lower surfaces of the substrate, and at least one of the first die and the second die being transparent to electromagnetic waves of a predetermined wavelength; a source of electromagnetic irradiation of the predetermined wavelength in order to heat an absorption layer arranged between the first template surface and the second template surface.

21. The device according to claim 20, wherein at least one of the first template surface and the second template surface is provided with the absorption layer.

22. The device according to claim 20, wherein the absorption layer is a metallic layer, a graphite layer or a layer of heat absorbing paint.

Description

BRIEF EXPLANATION OF THE FIGURES

[0026] The invention is described in greater detail below with reference to embodiments that are illustrated in the figures. The figures show:

[0027] FIGS. 1A-1C schematic representations of a method for forming a dimensionally stable three-dimensional shape into a sheet-like substrate of thermoplastic material;

[0028] FIG. 2 a schematic representation of the mould during irradiation from one side;

[0029] FIG. 3 a schematic representation of the mould during irradiation from both sides;

[0030] FIG. 4 a schematic representation of the method with the absorption layer provided on the substrate;

[0031] FIG. 5 a diaphragm manufacturable by the method of FIG. 1;

[0032] FIGS. 6A-6B schematic representations of a method for forming a dimensionally stable three-dimensional shape into a sheet-like substrate of thermoplastic material including bonding of two layers.

DESCRIPTION OF THE INVENTION

[0033] FIGS. 1A-1C show schematic representations of a method for forming a dimensionally stable three-dimensional shape into a sheet-like substrate 3 of thermoplastic material.

[0034] FIG. 1A shows an open mould with a first die 1 having a first template surface 11 and a second die 2 having a second template surface 21. The first template surface 11 having the inverse shape of the desired three-dimensional structure to be formed into an upper surface 31 of the sheet-like substrate 3. The second template surface 21 having the inverse shape of the desired three-dimensional structure to be formed into a lower surface 32 of the sheet-like substrate 3. The first and second template surfaces 11, 21 may have complementary shapes as shown in FIGS. 1A-1C and FIG. 2. However, non-complementary shapes are also possible as long as the thermoplastic material can be sufficiently displaced in its molten state, as shown in FIG. 3 and FIG. 4.

[0035] The sheet-like substrate 3 may be planar sheet, foil or film having a thickness in the range of 5 to 5000 micrometres, preferably 25 to 500 micrometres, and is placed between the first and the second die 1, 2. With respect to the present invention the sheet-like substrate before applying the method is two-dimensional. Afterwards it has a dimensionally stable three-dimensional shape e.g. with complementary corrugations to obtain e.g. a diaphragm with approximately the same overall thickness (FIG. 1C) or non-complementary corrugations (FIG. 3) to obtain e.g. a diaphragm with changing thickness.

[0036] Good results have been achieved so far with a 25 micrometer film of poly ether ether ketone (PEEK). However, thicker films and other materials, such as polybenzimidazole (PBI), polyimide (PI), thermoplastic polyimide (TPI), polyamide imide (PAI), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI), polysulfone (PSU), polyether ketone (PEK), polyaryl ether ketone (PAEK), polyphenylene sulfide (PPS), perfluoroalkoxy polymer (PFA), ethylenetetrafluoroethylene (ETFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF) or polybutylene terephthalate (PBT) may also be used.

[0037] In the method shown in FIGS. 1A-1C the first template surface 11 of the first die 1 is provided with an absorption layer 5. The absorption layer 5 can be quickly heated within milliseconds by electromagnetic irradiation 4 of a wavelength in the range of 200 to 2000 nm from a pulsed source. In order to irradiate the absorption layer 5, the first die 1 is of a material transparent to the wavelength of the electromagnetic irradiation 4.

[0038] After or during closure of the mould (FIG. 1B), the absorption layer 5 absorbs the irradiation 4 and is quickly heated up in order to transfer the energy to the thermoplastic sheet-like substrate 3. The substrate 3 is thereby heated until it is sufficiently hot, typically to or above its glass transition temperature, to be transformed into the desired three-dimensional shape. During the process the first and/or second die 1, 2 of the mould hardly heat up and almost immediately after stopping the irradiation 4 the mould can be opened and the transformed sheet-like substrate 3 can be removed (see FIG. 1C). The mould is then ready for the next cycle.

[0039] Alternatively to the embodiment shown in FIGS. 1A-1C, the second die 2 and the sheet-like substrate 3 may be transparent to the irradiation. In this case the irradiation can pass through the second die 2 and the substrate 3 to the absorption layer 5 provided on the first die 1, as shown in FIG. 2.

[0040] In order to process thicker sheet-like substrates, both the first and the second template surfaces 11, 21 may each be provided with an absorption layer 5, 5. In this case both the first and second die 1, 2 are transparent and the absorption layers 5, 5 are irradiated from opposite sides, as shown in FIG. 3.

[0041] FIG. 4 shows a variation of the method where the sheet-like substrate 3 itself is provided with an absorption layer 5 coated onto the substrate on one side or both sides or the substrate is of thermoplastic material that absorbs the irradiation. The first and/or the second die 1, 2 are transparent and the irradiation can be directed onto the substrate from one or both sides.

[0042] FIG. 5 shows an example of an article that may be manufactured with the method according to the invention. The article is a diaphragm 6 made of thermoplastic film material as it is described in WO2016012233. The diaphragm 6 in form of a disc comprises a plurality of concentric corrugations 61 and radial reinforcing ribs 62. Such a three-dimensional structure may be obtained by the methods described above. Good results have been achieved e.g. with a planar 25 micrometre thick PEEK film, into which a plurality of circular, concentric corrugations such as shown in the diaphragm of FIG. 5 have been formed.

[0043] As shown in FIGS. 6A-6B, the method further allows to bond two or more layers of substrate 3, 3a together. FIG. 6A shows the mould in the open state before transforming the substrates 3, 3a. FIG. 6B shows the mould in the open state after transforming the substrate to a substrate with dimensionally stable three-dimensional shape 3. In order to obtain e.g. a diaphragm with a plurality of concentric corrugations and an central part, which is several times thicker than the corrugated diaphragm, a separate part 3a of substrate can be placed centrally on the sheet-like substrate 3, as indicated in FIG. 6A, or placed in one of the two dies 1, 2. An example of such a diaphragm is described in Swiss patent application No. 00038/16.

[0044] The separate part 3a may be constituted as an absorption layer 5a or may be provided with an absorption layer 5a on either side. During irradiation of the absorption layer(s) 5, 5a the two substrate parts 3, 3a are heated above the glass transition temperature of the thermoplastic material and thereby permanently bonded together and a dimensionally stable three-dimensional shape is formed into the sheet-like substrate 3, as shown in FIG. 6B.

[0045] It is understood that the present invention is not limited to the embodiments as discussed above. The person skilled in the art will be able to derive further variants with knowledge of the invention which also belong to the subject matter of the present invention.

REFERENCE SIGNS

[0046] 1 first die [0047] 11 first template surface [0048] 2 second die [0049] 21 second template surface [0050] 3 sheet-like substrate [0051] 3a part of sheet-like substrate [0052] 3 transformed sheet-like substrate [0053] 31 upper surface [0054] 32 lower surface [0055] 4, 4 electromagnetic irradiation [0056] 5, 5 absorption layer [0057] 5a absorption layer [0058] 6 diaphragm [0059] 61 concentric corrugations [0060] 62 radial ribs