Abstract
The invention relates to a film body, a method for the back-injection molding of a film body and a back-injection molding tool therefor. In particular, the invention relates to a method for the back-injection molding of layer electrodes (1) for producing touch-sensitive sensors for example for touch screens. Parts of the layer electrode (1), which after the back-injection molding should still be able to move freely, are covered by a sacrificial film (3) before and during the back-injection molding.
Claims
1. A method of molding a layer electrode for producing a touch-sensitive sensor, wherein said layer electrode includes at least one tail portion that is not to be back-injection molded, said method comprising: (a) covering said at least one tail portion with a sacrificial film; (b) introducing said layer electrode and said sacrificial film into a back-injection molding tool, wherein said back-injection molding tool contains a back-injection molding material; (c) back-injection molding said layer electrode and said sacrificial film to produce a back-injection molded body, wherein during said back-injection molding, said sacrificial film binds to said back-injection molding material, and said at least one tail of said layer electrode lies on said sacrificial film and can be moved freely; and (d) forming a touch-sensitive sensor from said produced back-injection molded body.
2. The method of claim 1 wherein said back-injection molding tool has an opening according to the dimensions, contour, and/or location of said back-injection molding tool, whereby there is provided a minimized amount of back-injection molding material between said at least one tail and said sacrificial film.
3. The method of claim 1 wherein said touch-sensitive sensor is formed from said back-injection molded body by applying a laser to said back-injection molded body, whereby said laser cuts said back-injection molded body to form said touch-sensitive sensor.
4. The method of claim 1 wherein said sacrificial film has approximately the same shape and the same surface area as said tail.
5. The method of claim 1 wherein said sacrificial film is a protective strip.
6. The method of claim 1 wherein said back-injection molded body has an area free of said layer electrode, and wherein said sacrificial film projects beyond said area free of said layer electrode.
7. The method of claim 1 wherein step (b) comprises fixing said layer electrode into said back-injection molding tool with at least one first vacuum line, and fixing said sacrificial film in said back-injection molding tool.
8. The method of claim 7 wherein said sacrificial film is fixed in said back-injection molding tool with at least one second vacuum line.
9. The method of claim 8 wherein said at least one first vacuum line and said at least one second vacuum line are controlled independently of each other.
10. The method of claim 1 wherein said sacrificial film is transparent.
11. The method of claim 1 wherein said sacrificial film has a thickness of from 1 m to 250 m.
12. The method of claim 1 wherein said at least one tail of said layer electrode is covered, and the covering of said at least one tail is formed by folding said sacrificial film along a folding strip.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The invention now will be described with respect to the drawings, wherein:
(2) FIG. 1 is a top perspective view of a first embodiment of a layer electrode in accordance with the present invention;
(3) FIG. 2A is another top perspective view of the layer electrode of FIG. 1; and FIG. 2B shows cross-sectional views of the layer electrode before (top) and after (bottom) back-injection molding;
(4) FIG. 3 is a top perspective view of a second embodiment of a layer electrode in accordance with the present invention;
(5) FIGS. 4A, 4B, and 4C are top perspective views of a third embodiment of a layer electrode in accordance with the present invention, before (FIG. 4A) and after (FIGS. 4B and 4C) back-injection molding, in which the layer electrode has a contour in the vicinity of the tail portion, wherein the contour matches that of the sacrificial film;
(6) FIGS. 5A and 5B show a method for manufacturing the film body for the layer electrode of FIGS. 1, 2A, and 2B, before the layer electrode is back-molded;
(7) FIGS. 6A and 6B are perspective views of forming the film body of the layer electrode from a sheet; and
(8) FIGS. 7A, 7B, and 7C depict the back-injection molding of a layer electrode using a back-injection molding tool having a fixing strip.
(9) The invention is explained in more detail below, with the help of figures, which show exemplary embodiments of the film body and of the back-injection molding tool.
(10) FIG. 1 shows a layer electrode 1 and a sacrificial film 3, which are inserted in a back-injection molding tool 2. The layer electrode 1 with the tail 7 is held by the vacuum line 8 formed in the back-injection molding tool 2, while the sacrificial film 3 is held by the second vacuum line 9 different therefrom. This is necessary because in this embodiment example, there is no coherent film body which comprises both the layer electrode 1, as well as the sacrificial film 3. Instead, here, the layer electrode 1, as first film, and the sacrificial layer 3, as second film, independent therefrom and only loosely arranged on top of each other, are present without connection between each other.
(11) The injection of the back-injection molding material for the formation of the back-injection molded body 10 (FIG. 2b) is carried out according to the embodiment shown in FIG. 1 by means of openings 4, 5 or 6. The directions, from which the back-injection molding material (not shown) arrives in the back-injection molding tool 2, are indicated here using black arrows. From the top, from direction 11, comes an offset arrow, which shows that the direction 11 is not a preferred direction from which the back-injection molding material is introduced into the back-injection molding tool 2 from FIG. 1. If, namely, the back-injection molding material came from this direction, then it could slide between the sacrificial film 3 and the layer electrode 1 or the tail 7 in the embodiment shown here and thus specifically lift the sacrificial film from the tail 7.
(12) In the embodiment example of FIGS. 2a and 2b, the sacrificial film 3 is present in combination with the layer electrode 1. FIG. 2a shows the top view on the film body made of layer electrode 1, tail 7 and sacrificial film 3. FIG. 2b then shows in cross-section the position of the film body from FIG. 2a in the back-injection molding tool 2 before the back-injection molding (FIG. 2b top) and after the back-injection molding (FIG. 2b bottom).
(13) The embodiment according to FIG. 2a is different from the embodiment from FIG. 1 in that here the sacrificial film 3 is joined to the layer electrode 1. For this reason, the second vacuum line 9 is dispensed with for fixing the sacrificial film 3 in the back-injection molding tool 2. The sacrificial film 3 is held on the layer electrode 1 as part of the film body made of layer electrode 1, tail 7 and sacrificial film 3 and fixed in the back-injection molding tool 2 with the layer electrode 1 and the tail 7 by means of the vacuum line 8. For example, the sacrificial film 3 is bonded to the layer electrode 1 by means of an additional layer, such as an adhesive layer (not shown).
(14) According to one embodiment, the sacrificial film 3 itself can be formed as adhesive layer, such that no additional layer is required. It is particularly important that the film body is joined such that the tail 7 can be removed from the sacrificial film 3 after the back-injection molding (FIG. 2b bottom). In the case that the sacrificial film 3 is formed as adhesive layer, this is stable and not sensitive to the conditions occurring during the back-injection molding, such as high temperatures etc.
(15) In the embodiment of the invention shown in FIG. 2a, the back-injection molding material comes preferably through the opening 11 of the back-injection molding tool 2, thus from above. In contrast, the two lateral openings 4 and 6, as well as the bottom opening 5 are less preferred because back-injection molding material could reach under the sacrificial film 3.
(16) It is finally shown in FIG. 2b how the back-injection molding proceeds in the back-injection molding tool 2.
(17) Firstly, the film body made of layer electrode 1, tail 7 and sacrificial film 3 is held at the top in the back-injection molding tool 2 by means of vacuum lines 8 (not shown in the cross-section). Then, the back-injection molding tool 2 is closed and the back-injection molding material is injected (not shown). After the back-injection molding had ended, a back-injection molded body 10 is present, on the upper side of which the layer electrode 1 is located, the tail 7 of which is not back-injection molded directly, but which is located on the sacrificial film 3 which is back-injection molded for its part. The materials are selected such that the tail 7 can be easily removed from the sacrificial film 3. This can also be the case if a sacrificial film 3, which is an adhesive film, is present.
(18) For example, for an embodiment of the invention according to FIGS. 2A and 2B, a sacrificial film 3 can be made of a material such as polyethylene (PE) and/or polyvinyl chloride (PVC), both characterized in that they have very smooth surfaces and are then back-injection molded with a back-injection molding material such as polymethyl methacrylate (PMMA), polycarbonate (PC), acrylonitrile butadiene styrene (ABS).
(19) The adhesion of the sacrificial film 3 to the layer electrode 1 can be in particular carried out also without adhesive, solely by means of van der Waals interaction.
(20) FIG. 3 shows an alternative embodiment to the film body, comprising the layer electrode 1, the tail 7 and the sacrificial film 3 from FIGS. 2A and 2B.
(21) To be seen again in FIG. 3 are the layer electrode 1, the vacuum line 8 of the back-injection molding tool 2, the tail 7, the sacrificial film 3 covering the latter and the openings 4, 5 and 6, which are unsuitable for the back-injection molding of this embodiment, as well as the suitable opening 11, from which the back-injection molding material comes in a suitable way during the back-injection molding of this embodiment.
(22) The embodiment of the invention shown in FIG. 3 is different from the one shown in FIG. 2a in that here the sacrificial film 3 is not joined to the layer electrode 1 by means of an additional layer or by means of an adhesive property of the sacrificial film 3 itself, but rather by means of an adhesive strip 25, which only joins the sacrificial film 3 to the layer electrode 1 in the connection area of layer electrode 1 with tail 7.
(23) Only an exemplary length of the adhesive strip 25 is shown here, this can also extend further over the entire length of the connecting line 26 of layer electrode 1 to the sacrificial film 3. The adhesive strip 25 can just as well also be located only in sections along the connecting line 26. The layer sequence of the film body shown here in FIG. 3 along the connecting line 26 can be thus described as follows: at the very bottom, the layer electrode 1 with the tail 7 which are held in the back-injection molding tool 2 by means of the vacuum lines 8. The sacrificial film 3, only loosely arranged, is located on it, and then over it is the adhesive strip 25, which joins the sacrificial film 3 to the layer electrode 1.
(24) Here too, like in the embodiment example from FIG. 2 the direction of injection 11 is preferred to the directions of injection 4, 5 and 6, because material injected from these openings could reach under the sacrificial film 3 and then the area which is to remain free the tail 7, in the illustrated example, would still be back-injection molded. FIGS. 4a, 4b and 4c show the sequence of an embodiment of the method according to the invention.
(25) As shown in FIG. 4a, the layer electrode 1 has the contour 22 in the vicinity of the tail 7. The contour 22 matches that of the sacrificial film 3 and is shown displaced in the representation only for reasons of simplicity. In the embodiment shown here, the sacrificial film 3 according to FIG. 2 is glued to the tail 7, either by means of an additional layer which glues both films together and/or in that the sacrificial film 3 itself has adhesive properties.
(26) In reality, the contours 22 in the embodiment match those of the sacrificial film 3, such that at the end of the layer electrode 1, where later the applied tail 7 is realized, a composite of the applied tail 7 of the layer electrode 1, the sacrificial film 3 and optionally another additional layer (not shown) is present. The outline of the tail 7, as it is present, for example, after the back-injection molding and cutting, is structured in the embodiment example shown here only after the back-injection molding.
(27) Because the contour 22 of the layer electrode 1 forms a bond with the sacrificial film 3 on three sides flush in the vicinity of the tail 7, back-injection molding material cannot reach between the two films and there is correspondingly here no preferred direction and/or preferred opening, from which the injection of the back-injection molding material is carried out.
(28) The layer electrode 1 after the back-injection molding can be seen in FIG. 4b. Thus a back-injection molded body 10 is formed according to the dimensions of the back-injection molding tool. This has an injection flap 14 which shows that the injection was carried out via opening 11 (FIG. 4a). A touch-sensitive sensor, comprising the back-injection molded layer electrode 1, is now cut out from the back-injection molded body 10. For this, for example, a laser structuring process is used. The tail 7 is not cut out yet, but rather it is only applied in the area 7. The tail 7 is formed by means of cutting, thus for example by applying a laser beam along the cutting line 12. Here, the laser intensity can be selected for example such that the laser beam cuts through at least the layer electrode 1 of approx. 50 m thickness, such that the contours of the tail 7 emerge. Alternatively, at increased laser intensity, for example the sacrificial film 3 can also be structured or cut. Alternatively or additionally, the injection flap 14 can also be cut off along the cutting line 13 by means of a correspondingly adjusted laser beam. The laser structuring can be carried out in one operation, wherein in each case different laser beam intensities are used for different cuts 12 or 13.
(29) The result of the method is shown in FIG. 4c: the tail 7 with the sacrificial film 3 placed behind it is formed; the injection flap 14 is removed. The back-injection molded body 10, the layer electrode 1 with tail 7 with the sacrificial film 3 placed behind it is to be seen. Thus, on the back-injection molded body 10 in the area of the tail 7, the sacrificial film 3 is first of all, and on top of this the tail 7, which can be removed from the sacrificial film 3 or which is only loosely placed on it.
(30) FIGS. 5a and 5b show by way of example a method for manufacturing the film body, for example according to FIGS. 2A and 2B, before it is back-injection molded.
(31) FIG. 5a shows a cut-out from an endless sheet of a film 15, from which a layer electrode 1 according to the invention is preferably formed. These films are known from DE 10 2009 014 575.8 and are preferably made of a polyolefin as transparent carrier material with a pattern made of conductive tracks, wherein the measurements of the tracks and the pattern formed by them are selected such that the film is conductive, but remains transparent for the human eye despite the non-transparent conductive tracks.
(32) On this endless sheet of film 15, a thin strip 16 is applied, from which the sacrificial films can be formed. In the direction of extension ER, this film composite from film 15 and strip 16 is for example kilometers long and wound up on a roll. The strip is advantageously structured and processed in the roll-to-roll method. For example, a laser beam with a first intensity is applied along a cutting line 17, in order to cut through the film 15 for example with a film thickness in the range of 30 m to 70 m. Thus layer electrodes 1 with tails 7 can be cut out from the strip. During the subsequent or previous cut with a laser beam of suitable intensity, the strip with the material for the sacrificial film 3, for example with a film thickness in the range of 50 m to 100 m, is cut through along the cutting line 18. Since in the area of the contours for the sacrificial film 3, the strip 16 and the sheet 15 must be cut through, a correspondingly suitable laser beam, which can cut both films, is to be selected here.
(33) According to the method, a film body, as is shown in FIG. 2a, can be produced. This is shown again in FIG. 5 b with layer electrode 1, tail 7 and sacrificial film 3.
(34) Alternatively, the film body can be produced from a sheet, as shown in FIGS. 6A and 6B. Here, a film, which comprises layer electrode 1, tail 7 and sacrificial film 3, is cut out from a layer. This film has a predetermined folding point 19, along which the film is folded over such that the sacrificial film 3, which initially adjoined the tail 7, lies on or under it. For this, the film is folded along the line 19 and in direction 20. After the back-injection molding was carried out, the folding strip 21 is cut off, for example by means of laser cutting, whereby the tail 7 is removed from the sacrificial film 3 without difficulty. In the back-injection molding tool 2 shown, this embodiment is then preferably back-injection molded from the direction of injection 5, because then the injection flap formed (not shown) can be cut off together with the folding strip 21.
(35) FIGS. 7a and 7b show a back-injection molding tool 2 with a strip fixing A, on which a protective strip 31 is attached, which assumes the function of the sacrificial film 3. As seen from FIG. 7b, when the back-injection molding tool 2 is closed, the protective strip 31 is arranged such that it is still attached to the strip fixing A, but it is arched such that at the point of the tail 7, it is applied to the latter as sacrificial film 3. Although the protective strip 31 is also back-injection molded during the back-injection molding, it can subsequently be pushed upwards out of its position, and thus expose a back-injection molded body 10, which comprises a back-injection molded layer electrode 1 and an exposed tail 7. The cavity in the back-injection molding tool 2, in which the back-injection molded body 10 is formed, is labeled 40.
(36) After the back-injection molding was carried out, the protective strip 31 is pushed out of the back-injection molding tool 2 and is available for a further back-injection molding process according to a preferred embodiment.
(37) For this, the protective strip 31 is advantageously equipped with a non-stick coating at least on one side. For example, the protective strip 31 has the non-stick coating on the side facing the back-injection molding material, such that the back-injection molding material does not adhere to the protective strip 31 and the removal can be carried out without difficulty.
(38) After several back-injection molding processes, the non-stick coating can be exhausted/used up. It can therefore be provided that the protective strip 31 is arranged on the strip fixings A as an endless roll such that it can be wound up. In each case after a few back-injection molding processes, the protective strip 31 can be wound forward and fresh film material is available as protective strip 31.
(39) FIG. 7c shows a variation of this embodiment of the method with the protective strip 31: flaps 32 a to 32 c, which serve as sacrificial films 3, are formed on the protective strip 31. On introducing the film body made of layer electrode 1 with tail 7 into the back-injection molding tool 2, precisely one of these flaps 32a to 32c of the protective strip 31 comes to lie on the tail 7. After the back-injection molding process, the flap 32b is cut off along the contour line 41. The cutting off is carried out for example by means of laser cutting, but can also be carried out by breaking a predetermined breaking point along the contour line 41, which is for example formed by means of a perforation provided there. Breaking such a predetermined breaking point along the contour line 41 can be caused for example simply by winding forward the protective strip 31.
(40) This embodiment is illustrated in FIG. 7c in that, before it is introduced into the back-injection molding tool 2, the protective strip 31 coming from the right has a flap 32a, which has a predetermined breaking point (not shown). The protective strip is wound to the left for the back-injection molding, such that the flap 32b is then back-injection molded together with the film body made of the layer electrode 1 and tail 7, wherein it covers the tail 7 as flap 32 b. After the back-injection molding, the protective strip 31 is wound further to the left via the endless rolls A for the strip fixing, wherein the predetermined breaking point breaks along the contour line 41 and thus the protective strip 31 displays only one other connection point 32c on the other side of the back-injection molding tool 2. The main part, referred to as flap 32 b, remains in this instance as sacrificial film 3 on the back-injection molded body 10 after the back-injection molding. For the subsequent back-injection molding process, a new flap 32a of the protective strip 31 is provided by further winding by means of the endless roll A.
LIST OF REFERENCE NUMBERS NO. 149
(41) 1. Layer electrode 2. Back-injection molding tool 3. Sacrificial film 4. Opening to the right for the intake of the back-injection molding material 5. Opening at the bottom for the intake of the back-injection molding material 6. Opening to the left for the intake of the back-injection molding material 7. Tail 8. Vacuum line layer electrode 9. Vacuum line sacrificial film 10. Back-injection molded body 11. Opening at the top for the intake of the back-injection molding material 12. Cutting line on the tail 7 13. Cutting line on the injection flap 14 14. Injection flap 15. Conductive film 16. Sacrificial film strip 17. Cutting line for layer electrode 1 and tail 7 18. Cutting line for sacrificial film 19. Predetermined fold line for folding 20. Direction of folding 21. Folding strip 22. Contour 25 Adhesive strip 26 Connecting line between sacrificial film 3 and layer electrode 1 31 Protective strip 32 Flap on the protective strip 40 Cavity 41 Contour line on the flap 32 of the protective strip 31 A Strip fixing A Endless roll for the strip fixing
