Texturizing and thermoforming process for a film giving the appearance of a garment part

Abstract

A texturizing and thermoforming process for an appearance film (2) with a substrate (10) and a coating (12), the glass transition temperature Tvs of the substrate being higher than the glass transition temperature Tvr of the coating, comprising the steps of providing a thermoforming cavity (16), the cavity (16) being the negative of the shape to be imparted to the film (2), and the wall (18) of the cavity (16) having a grain (20) which is the negative of the texture (22) to be imparted to the film, heating the film to a temperature that is higher than Tvr and lower than Tvs, pushing the film against the wall (18) to texture it, while the film (2) is held against the wall (18), further heating the film (2) to a temperature above Tvs to set the film (2) in its final shape, and cooling and removing the film. Abstract figure: Figure 2

Description

Title of the invention: Method for texturizing and thermoforming a film for the appearance of a trim part Technical field

[0001] The present disclosure relates to the field of injection molding of trim parts for motor vehicles, such as dashboards, door panels or the like.

[0002] In this field, we are particularly interested in film insert molding (FIM) processes which make it possible to produce molded trim parts with varied decoration.

[0003] Also of interest here are in-mold electronics (IME) processes that allow conductive tracks and electronic components to be incorporated into the molded trim part. This results in "intelligent" trim parts, i.e. trim parts with integrated functionalities.

[0004] In both types of process, the film insertion molding process, as well as the in-mold electronics process, the resulting trim pieces consist of a surface film that forms the visible external surface of the trim piece, and an overmolded structural support that carries the surface film.

[0005] The present disclosure relates particularly to the shaping of the appearance films used during film insertion molding or during in-mold electronics processes. Typically, these appearance films are thermoformed to give them a three-dimensional shape which corresponds to that of the desired trim part. The appearance films are also textured in order to ensure a well-defined matt finish of the trim parts incorporating them. Prior art

[0006] In this context, document US 2008 / 0193684 A1 describes a particular process for shaping an appearance film in which the appearance film is thermoformed and textured at the same time during the same step. This process is known by the English term "in-mold graining process".

[0007] This known process has the disadvantage that the texturization of the appearance film is not always well controlled.

[0008] Document US 2009 / 0130401 A1 describes in its §§ 10 to 13 a method of injection molding a covering part with an appearance film. In this method, the texturization of the appearance film takes place during the final step of injecting the plastic material into the injection mold, and not during a possible prior step of thermoforming of the appearance film.

[0009] This second known process also does not allow for good control of the texturization of the appearance film, in particular due to the high temperatures reached during the injection of the plastic material into the injection mold. Summary

[0010] Consequently, an aim of the present disclosure is to propose a method for shaping an appearance film for a motor vehicle trim part which makes it possible to texturize the appearance film in a well-controlled manner.

[0011] In particular, it is a question of being able to increase the precision and reproducibility of texturing.

[0012] According to the present disclosure, this aim is achieved with a method for texturizing and negative thermoforming an appearance film for a vehicle trim part, the appearance film comprising a substrate and a coating at least partially covering the substrate, the glass transition temperature Tvs of the substrate being higher than the glass transition temperature Tvr of the coating, the method comprising the steps of providing a thermoforming mold having a thermoforming cavity defined by a wall, the wall of the thermoforming cavity having a grain, the grain being the negative of a texture to be imparted to the appearance film, positioning the appearance film opposite the thermoforming cavity, the coating of the appearance film being turned towards the thermoforming cavity,heating the appearance film to a first temperature Tl higher than the glass transition temperature Tvr of the coating and lower than the glass transition temperature Tvs of the substrate to make the coating susceptible to plastic deformation, the substrate remaining solid, texturizing the coating by pushing the appearance film, by elastic deformation of the substrate, against the wall of the thermoforming cavity, to print the coating of the grain of the wall, heating the appearance film to a second temperature T2 higher than the glass transition temperature Tvs of the substrate while the appearance film is held against the wall of the thermoforming cavity, to transform the elastic deformation of the substrate into a plastic deformation, cooling the textured and thermoformed appearance film, and removing the textured and thermoformed appearance film from the thermoforming mold.

[0013] This method is innovative in particular in that it uses an appearance film with a substrate and a coating which has a glass transition temperature lower than that of the substrate, and in that it provides for subjecting this appearance film to a particular thermoforming in which the texturization is carried out in the coating during a dedicated step and at a dedicated temperature.

[0014] Indeed, thanks to this more sophisticated thermoforming, we are able to control the texturization precisely, since it takes place separately at a temperature well adapted.

[0015] The features set out in the following paragraphs may optionally be implemented. They may be implemented independently of one another or in combination with one another: - during the steps of texturizing and heating the appearance film to a 2nd temperature T2, the appearance film is pushed and held against the wall of the thermoforming cavity by pressure exerted on the substrate by compressed air; - the substrate of the appearance film comprises polycarbonate and / or polymethyl methacrylate; - the substrate of the appearance film is transparent in the visible; - the coating of the appearance film comprises an acrylic varnish, preferably reticulated; - the glass transition temperature Tvr of the coating is between 75°C and 95°C, and the glass transition temperature Tvs of the substrate is between 135°C and 150°C; - the first temperature T1 is between 76°C and 110°C, and the second temperature T2 is between 136°C and 170°C; - the maximum depth of the texture of the textured and thermoformed appearance film is less than the coating thickness defined before the coating texturization step.

[0016] The present disclosure also relates to a method of manufacturing a vehicle trim part, the trim part having a main body provided with an appearance film, the method comprising the steps of providing an appearance film comprising a substrate and a coating at least partially covering the substrate, applying the method defined above to the provided appearance film in order to texturize and thermoform it, inserting the textured and thermoformed appearance film into a cavity of an injection mold, and forming the main body provided with the appearance film by injecting a thermoplastic material into the cavity of the injection mold, to obtain the trim part.

[0017] Preferably, conductive tracks are arranged on the substrate of the appearance film provided in the step of providing the appearance film.

[0018] Furthermore, it is possible to provide, after the texturization and thermoforming of the appearance film and before its insertion into the injection mold, the additional step of placing electronic components on the rear face of the substrate of the textured and thermoformed appearance film, in line with the conductive tracks arranged on the appearance film. Brief description of the drawings

[0019] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which: Fig.l

[0020] [Fig.l] shows a “smart” trim piece according to one embodiment of the present disclosure. Fig. 2

[0021] [Fig.2] shows an embodiment of a method for shaping a film appearance according to the present disclosure. Description of the embodiments

[0022] The method which will be described below is a method of manufacturing a trim part for a motor vehicle.

[0023] The trim piece to be manufactured may, for example, be a dashboard or a door panel.

[0024] With reference to [Fig.l], this type of covering part 1 comprises an appearance film 2 which forms the visible external surface of the covering part 1, and a structural support 4 overmolded on the appearance film 2. The structural support 4 can also be described as the main body of the covering part 1.

[0025] In the example chosen, the trim part 1 to be manufactured is a so-called “intelligent” trim part. It is a trim part that integrates functional zones, such as for example touch zones 6. The touch zones 6 form a user interface. This interface allows a user to control functionalities of the motor vehicle in which the trim part 1 is mounted.

[0026] In the context of the present disclosure, such "smart" trim pieces are also referred to as plastronic trim pieces. These plastronic trim pieces are plastic trim pieces with integrated electronic components. Such a plastronic trim piece has electronic components that are embedded in its plastic material. A set of conductive tracks connecting the electronic components is incorporated into the plastronic trim piece.

[0027] A plastronic trim piece not only serves as decoration and trim for the motor vehicle, but also allows the occupant of the motor vehicle to adjust certain functions of the latter by interacting with the plastronic trim piece.

[0028] In the plastronic cladding part 1 shown in [Fig.l], the electronic components are identified by the reference 8. The conductive tracks, which electrically connect the electronic components 8 together, are arranged on the appearance film 2.

[0029] The electronic components 8 may for example be light-emitting diodes. These light-emitting diodes then serve as backlighting. With their light, they highlight the touch-sensitive areas 6 to allow the user to identify them. In this case, the aspect film 2 is transparent in the visible to allow the transmission of the light emitted by the light-emitting diodes 8 to the passenger compartment of the motor vehicle.

[0030] Preferably, the main body 4 is made of thermoplastic material.

[0031] The film of appearance 2 comprises a substrate 10 and a coating 12 covering at least part of the substrate 10. The coating 12 covers, for example entirely, a front face of the substrate 10. By “front” face, we mean for example a face intended to be turned towards the passenger compartment of the vehicle.

[0032] Preferably, the coating 12 is uncovered, that is to say it is exposed to the environment. In this case, the coating 12 is therefore in the open air, and no additional layer covers it.

[0033] Preferably, the thickness of the coating 12 is constant over its entire extent before the step of texturizing the coating 12.

[0034] Here, the conductive tracks are arranged, preferably printed, on the substrate 10. In particular, they can be arranged on a rear face 11 of the substrate 10.

[0035] Preferably, the substrate 10 of the appearance film 2 comprises polycarbonate (PC) and / or polymethyl methacrylate (PMMA). The substrate 10 of the appearance film 2 is for example made of polycarbonate (PC), polymethyl methacrylate (PMMA), or a combination of PC and PMMA. The coating 12 of the appearance film 2, for its part, preferably comprises an acrylic varnish. The coating 12 of the appearance film 2 is for example made of an acrylic varnish. Advantageously, the coating 12 can be crosslinked to increase its hardness.

[0036] In order to allow the light generated by some of the electronic components 8 to pass through, the substrate 10 and the coating 12 may be transparent in the visible range, at least at the level of backlit areas of the plastronic covering part 1. For example “transparent” means having a visible light transmission rate greater than 5%, preferably greater than 20%.

[0037] Furthermore, the film of appearance 2 comprises for example a layer of opaque ink arranged on the substrate 10, the backlit areas being devoid of the layer of opaque ink. By “opaque” is meant having a visible light transmission rate of less than 5%, for example equal to 0%.

[0038] To meet the needs of the manufacturing method described below, the materials of the substrate 10 and of the coating 12 are chosen so that the glass transition temperature Tvs of the substrate 10 is higher than the glass transition temperature vitreous Tvr of coating 12.

[0039] It is preferable that the glass transition temperature Tvr of the coating 12 is between 75°C and 95°C. For example, the glass transition temperature Tvr of the coating 12 may be approximately 80°C.

[0040] Preferably, the glass transition temperature Tvs of the substrate 10 is between 135°C and 150°C. For example, the glass transition temperature Tvs of the substrate 10 may be approximately 140°C.

[0041] As will be seen below during the description of the manufacturing process, this difference in glass transition temperature between the coating 12 and the substrate 10 makes it possible to better control the texturization of the film of appearance 2.

[0042] By way of example, the thickness of the substrate 10 is at least 250 qm, for example less than 600 qm and the thickness of the coating 12 is at least 3 qm, for example less than 20 qm. Thus, the coating 12 is significantly thinner than the substrate 10. Preferably, the thickness of the coating 12 is only a few percent of the thickness of the substrate 10. By way of example, the thickness of the coating 12 represents between 0.5% and 8% of the thickness of the substrate 10.

[0043] A method, in accordance with the present disclosure, for manufacturing the plastronic covering part 1 shown in [Fig.l] will now be described.

[0044] The manufacturing process begins with the provision of the film of appearance 2. The film of appearance 2 is provided in the form of a flat sheet, for example rectangular. This flat sheet 2 is visible in Figure 2b.

[0045] The manufacturing process then continues with a step of texturizing and thermoforming the film of appearance 2. It is this step which is at the heart of the present disclosure. It constitutes a process of texturizing and negative thermoforming the film of appearance 2. This is illustrated by Figures 2a to 2f. The process in question thus comprises six sub-steps a to f, each of which corresponds to one of Figures 2a to 2f.

[0046] In sub-step a, cf. figure 2a, a thermoforming mold 14 is provided. The mold 14 has a thermoforming cavity 16 defined by a wall 18. The general shape of the wall 18 of the thermoforming cavity 16 is the negative of the three-dimensional shape to be imparted to the film of appearance 2. It will be noted that the wall 18 of the thermoforming cavity 16 has a grain 20 which is the negative of the texture to be imparted to the film of appearance 2. The grain 20 preferably has a maximum depth less than the thickness of the coating 12.

[0047] Here, the maximum depth of grain 20 is understood to mean the distance between the highest point and the most remote point of grain 20, taken in a direction perpendicular to the general shape of wall 18.

[0048] In the following sub-step b, see Figure 2b, the flat-appearing film 2 is arranged in face of the thermoforming cavity 16. The coating 12 of the flat-appearing film 2 is then turned towards the thermoforming cavity 16.

[0049] During the following sub-step c, cf. figure 2c, the film of appearance 2 is heated to a first temperature Tl which is higher than the glass transition temperature Tvr of the coating 12 and lower than the glass transition temperature Tvs of the substrate 10. This first temperature Tl can be between 76°C and 110°C.

[0050] For example, if the glass transition temperature Tvr of the coating 12 is 80°C, and the glass transition temperature Tvs of the substrate 10 is 140°C, then the first temperature Tl could be about 100°C. In other words, at the end of sub-step c, the temperature Tl of the film of appearance 2 is between the glass transition temperature Tvr of the coating 12 and the glass transition temperature Tvs of the substrate 10. The sub-step has the effect of softening the coating 12, since its glass transition temperature Tvr is exceeded. On the other hand, the substrate 10 remains solid, since its glass transition temperature Tvs is not exceeded. Bringing the film of aspect 2 to this intermediate temperature T1 makes it possible to shape the coating 12 by plastic deformation, without impact on the substrate 10. The shaping of the coating 12 is the subject of the following sub-step d.

[0051] In sub-step d, cf. figure 2d, the film of aspect 2 is pushed, by elastic deformation of the substrate 10, against the wall 18 of the thermoforming cavity 16. This thrust is illustrated in figure 2d by the set of arrows F. In this way, the film of aspect 2 is deformed and takes on the three-dimensional shape of the thermoforming cavity 16. It will be noted that at this stage, the deformation of the film of aspect 2, by its elastic nature, is only temporary and reversible. In the absence of the pressure exerted on the film of aspect 2 by the thrust F, the film of aspect 2 would immediately return to its planar shape visible in figures 2b and 2c. Indeed, in sub-step d, the temperature of the film of appearance 2 is still at temperature Tl, that is to say at a temperature below the glass transition temperature Tvs of the substrate 10.

[0052] As visible in Figure 2d, the soft coating 12 is forced against the wall 18 of the thermoforming cavity 16. Thus, the soft coating 12 is imprinted with the grain 20 of the wall 18. Since the temperature of the film of appearance 2 is higher than the glass transition temperature Tvr of the coating 12, the latter is susceptible to plastic deformation. A well-controlled texture 22 is thus obtained on the external surface of the film of appearance 2. The texture 22 obtained may in particular be rough so that the film of appearance 2 reflects light in a diffuse manner. In this case, thanks to the texture 22, the mattness of the film of appearance 2 is optimized. The texture 22 preferably has a maximum depth less than the thickness of the coating 12.

[0053] Here, the maximum depth of the texture 22 is understood to mean the distance between the highest point and the most remote point of the texture 22, taken in a direction perpendicular to the dicular to a surface of the substrate 10 of the film of aspect 2.

[0054] The exact characteristics of the texture 22 depend on the type of grain 20 of the surface 18 of the thermoforming cavity 16. The grain 20 of the thermoforming cavity 16 is chosen according to the texture of the desired appearance film 2. The grain 20 is obtained for example by mechanical or chemical treatments of the wall 18 of the thermoforming cavity 16.

[0055] Once the coating 12 has been textured, we then continue with sub-step e, see FIG. 2e. In this step, while the film of appearance 2 is held against the wall 18 of the thermoforming cavity 16, the film of appearance 2 is further heated to a second temperature T2 beyond the glass transition temperature Tvs of the substrate 10. This second temperature T2 can be between 136°C and 170°C.

[0056] The second temperature T2 may for example be approximately 160°C. Consequently, the substrate 10 also softens. It therefore also loses its strength and becomes susceptible to plastic deformation. This can be seen in Figure 2e. The film of aspect 2 is now completely soft and the elastic deformation of the substrate 10 transforms into plastic deformation. Thus, the film of aspect 2 is in its final three-dimensional shape. It is during this sub-step e that the thermoforming of the film of aspect 2 takes place.

[0057] Preferably, the film of aspect 2 is pushed and held against the wall 18 of the thermoforming cavity 16 by a pressure exerted on the substrate 10 by compressed air. In this case, the film of aspect 2 is forced into the thermoforming cavity 16 by a flow of compressed air which is sent against the rear face 11 of the substrate 10. This is illustrated by the arrows F in FIGS. 2d and 2e. The term "rear face" of the substrate is understood to mean the face opposite the face on which the coating 12 is arranged. Preferably, the pressure exerted by the compressed air is greater than 80 bars. This deformation method is known as high pressure forming (HPF).

[0058] Once the aspect 2 film is in its final three-dimensional form, the last sub-step f is then carried out, see Figure 2f. This consists of cooling the textured and thermoformed aspect 2 film, and removing it from the thermoforming mold 14. The resulting aspect 2 film is shown in Figure 2f.

[0059] The step of cooling the film of appearance 2 is carried out when the textured and thermoformed film of appearance 2 is against the wall 18 of the thermoforming cavity 16. During the cooling step, the temperature of the film of appearance 2 falls below the glass transition temperature Tvs of the substrate 10 and then below the glass transition temperature Tvr of the coating 12. The film of appearance 12 is therefore rigid at the end of the cooling step. After the cooling step, the film of appearance 2 is fixed in its final three-dimensional shape.

[0060] With this improved texturizing and thermoforming method, the texturizing of the appearance film takes place separately from the thermoforming of the appearance film. The coating 12 of the appearance film 2 is first texturized (sub-step d), then the entire appearance film 2 is thermoformed (sub-step e). The texturizing and thermoforming therefore take place sequentially and not in parallel. This procedure makes it possible to texturize the appearance film 2 in a more precise and controlled manner.

[0061] Preferably, the duration of all sub-steps b to f is between 30 and 50 seconds. The duration of all sub-steps c to e may be between 15 and 30 seconds.

[0062] Once the film of aspect 2 is textured and thermoformed, one can then continue with the next step of the manufacturing process of the covering part 1. This consists of inserting the textured and thermoformed film of aspect 2 into a cavity of an injection mold.

[0063] The step of inserting the appearance film 2 into the injection mold is followed by a step of forming the main body 4 of the covering part 1 by injecting a thermoplastic material into the cavity of the injection mold, in particular on the rear face 11 of the substrate 10 of the appearance film 2. Thus, the appearance film 2 is overmolded with the thermoplastic material, and the covering part 1 is obtained.

[0064] If one wishes to manufacture a plastronic cladding part such as shown in [Fig.l], it is then first necessary to place the electronic components 8 on the rear face 11 of the substrate 10 of the appearance film 2, in line with the conductive tracks incorporated in the appearance film 2, before proceeding with the overmolding. During overmolding, the electronic components 8 are embedded in the thermoplastic material.

[0065] Of course, the present disclosure is not limited to the manufacture of plastronic trim parts. In particular, the texturizing and thermoforming process shown in Figures 2a to 2f can also be used in the production of other types of trim parts, for example purely decorative trim parts.

Claims

Claims

1. Method for texturizing and negative thermoforming an appearance film (2) for a vehicle trim part (1), the appearance film (2) comprising a substrate (10) and a coating (12) at least partially covering the substrate (10), the glass transition temperature Tvs of the substrate (10) being higher than the glass transition temperature Tvr of the coating (12), the method comprising the steps of: a. providing a thermoforming mold (14) having a thermoforming cavity (16) defined by a wall (18), the wall (18) of the thermoforming cavity (16) having a grain (20), the grain (20) being the negative of a texture (22) to be imparted to the appearance film (2); b. positioning the appearance film (2) opposite the thermoforming cavity (16), the coating (12) of the appearance film (2) being turned towards the thermoforming cavity (16); c. heating the appearance film (2) to a first temperature Tl higher than the glass transition temperature Tvr of the coating (12) and lower than the glass transition temperature Tvs of the substrate (10) to make the coating (12) susceptible to plastic deformation, the substrate (10) remaining solid; d. texturizing the coating (12) by pushing the appearance film (2), by elastic deformation of the substrate (10), against the wall (18) of the thermoforming cavity (16), to print the coating (12) of the grain (20) of the wall (18); e. heating the appearance film (2) to a second temperature T2 higher than the glass transition temperature Tvs of the substrate (10) while the appearance film (2) is held against the wall (18) of the thermoforming cavity (16), to transform the elastic deformation of the substrate (10) into a plastic deformation; and f. cooling the textured and thermoformed appearance film (2), and removing the textured and thermoformed appearance film (2) from the thermoforming mold (14).

2. Method according to the preceding claim, in which, during the steps of and e, the appearance film (2) is pushed and held against the wall (18) of the thermoforming cavity (16) by pressure exerted on the substrate (10) by compressed air (F).

3. A method according to any preceding claim, wherein the substrate (10) of the appearance film (2) comprises polycarbonate and / or polymethyl methacrylate.

4. Method according to any one of the preceding claims, in which the substrate (10) of the appearance film (2) is transparent in the visible.

5. Method according to any one of the preceding claims, in which the coating (12) of the appearance film (2) comprises an acrylic varnish, preferably crosslinked.

6. A method according to any preceding claim, wherein the glass transition temperature Tvr of the coating (12) is between 75°C and 95°C, and the glass transition temperature Tvs of the substrate (10) is between 135°C and 150°C.

7. The method of claim 6, wherein the first temperature T1 is between 76°C and 110°C, and the second temperature T2 is between 136°C and 170°C.

8. Method according to any one of the preceding claims, in which the maximum depth of the texture (22) of the textured and thermoformed appearance film (2) is less than the thickness of the coating (12) defined before step d of texturizing the coating (12).

9. A method of manufacturing a trim part (1) for a vehicle, the trim part (1) having a main body (4) provided with an appearance film (2), the method comprising the steps of: a. providing an appearance film (2) comprising a substrate (10) and a coating (12) at least partially covering the substrate (10); b. applying the method according to any one of the preceding claims to the provided appearance film (2) in order to texturize and thermoform it; c. inserting the textured and thermoformed appearance film (2) into a cavity of an injection mold; and d. forming the main body (4) provided with the appearance film (2) by injecting a thermoplastic material into the cavity of the injection mold, to obtain the trim part (1).

10. Method according to the preceding claim, in which conductive tracks are arranged on the substrate (10) of the appearance film (2) provided in step a of providing the appearance film (2).

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