FR3066432A1 - MOTOR VEHICLE PART COMPRISING A DECORATIVE SURFACE FILM - Google Patents

Abstract

The invention relates to a motor vehicle part (2) made of plastic material characterized in that it comprises: - an at least partially transparent main body (4), - a transparent surface film (6) comprising two faces (10 12) opposite one another with at least one relief (8) formed on each of the two faces (10, 12), and - a transparent adhesive layer (14) arranged between the main body (4) and the surface film (6), the main body (4), the surface film (6) and the adhesive layer (14) are made of materials capable of diffracting the light rays at least twice, once when the rays light reaches one of the faces (10, 12) of the surface film (6) and a second time when the light rays reach the other face (10, 12) of the surface film.

Description

The invention relates to motor vehicle parts made of plastic and more particularly the integration of three-dimensional effect surface films on such parts.

These surface films are films made of plastic. They include one or more layers of plastic (for example an inner layer (called matrix) of polyurethane and decorative layers of polyamide) transparent. The decorative layers form the external faces of the film and for this purpose carry one or more reliefs making it possible to obtain a depth effect, called above "three-dimensional effect". It is a lenticular effect. The reliefs can be obtained by stamping (or embossing) the faces of the surface film.

An example of such a surface film is described in patent AT 511,083 B1.

These surface films are currently present on various equipment, in particular sports equipment (for example skis), in order to optimize the visual rendering of this equipment by being placed on the latter, for example on the face of skis bearing the mark of maker.

In order to obtain an optimal visual effect, an impression is made on the face of the surface film intended to be in contact with the equipped part. It can for example be a screen printing.

The phenomenon observed is as follows: the light flux reaching the surface film (called the incident ray) is partly refracted during its passage through the surface film. The part of the refracted light flux then reaches the face of the film in contact with the equipped part (that is to say the face having undergone printing) and will be reflected by the printed layer. The luminous flux then crosses the surface film in the direction of the face opposite to the part (that is to say the entry face). The luminous flux then leaves the surface film (we speak of an emerging ray) by undergoing a second refraction. The angles of refraction and reflection of the light rays are different depending on the area of the relief in interaction with the light rays. The positioning of the reliefs with respect to each other on either side of the film makes it possible to obtain an optimal visual effect.

This solution has a major drawback. Indeed, if the equipped part is a transparent part, then the surface film does not allow this transparency of the part to be preserved because of the printing carried out on one of the faces of the surface film. In other words, the technique implemented to obtain a quality visual effect alters the initial appearance of the equipped room.

In addition, printing requires a step of resuming the surface film after manufacture, which requires time and generates significant costs due to the printing techniques to be implemented, for example by not depositing ink dots. only at strategic locations to obtain an optimal optical effect.

It could then be possible not to print on the surface film and to fix it directly on a part.

However, this solution also has a major drawback. Auto parts made of transparent plastic are made of a material identical to that of the surface film. Consequently, the light flux reaching the face of the surface film in contact with the equipped part continues its race in the equipped part in a direction identical to the direction of propagation of the light flux in the surface film. This has the consequence of greatly degrading the desired depth effect or even canceling it out because the light rays no longer undergo refraction when they pass the surface film in the equipped room.

In the case of an opaque plastic part, the light flux is absorbed by the part which also leads to the degradation, or even to the cancellation of the desired depth effect.

In other words, the relief present on the face of the surface film in contact with the equipped part no longer has an impact on the trajectory of the light rays and therefore on the visual effect obtained.

An object of the invention is therefore to provide a part of a motor vehicle comprising a three-dimensional effect surface film making it possible both to maintain an optimal optical effect while retaining the transparent appearance of the equipped part.

The subject of the invention is a motor vehicle part made of plastic material, characterized in that it comprises:

- a main body at least partially transparent,

- a transparent surface film comprising two faces opposite one another with at least one relief produced on each of the two faces, and

a transparent adhesive layer disposed between the main body and the surface film, the main body, the surface film and the adhesive layer being made of materials capable of refracting the light rays at least twice, a first time when the rays light reaches one side of the surface film and a second time when the light rays reach the other side of the surface film.

Thus, a part is obtained retaining an optimal optical effect thanks to at least two refractions when the light flux crosses the surface film right through while avoiding an impression of the face of the surface film in contact with the main body, this which keeps the transparency of the room. This lack of recovery for printing also saves time and saves money during the production of the parts, a non-negligible element in the case of parts having to be manufactured while respecting an industrial rate.

Optionally, the motor vehicle part may include one or more of the following characteristics:

the main body is made of a material having a refractive index different from that of the surface film;

- the adhesive layer has a refractive index different from that of the main body;

- the adhesive layer has a refractive index different from that of the surface film;

the adhesive layer comprises an acrylic adhesive;

- the relief includes bosses; and

- the main body (4) is made of polymethyl methacrylate.

According to the invention, a motor vehicle is also provided comprising a part according to the invention.

We will now present several embodiments of the invention given by way of nonlimiting examples and with the support of the appended figures in which:

- Figures 1A and 1B are respectively partial schematic sectional and front views of a motor vehicle part according to the invention;

- Figure 1C is an enlargement of an area of the part of Figures 1A and 1B;

- Figures 2A and 2B are respectively partial schematic sectional and front views of an alternative embodiment of the invention; and

- Figure 2C is an enlargement of an area of the part of Figures 2A and 2B;

FIGS. 1A to 2C represent a part 2 of a motor vehicle made of plastic and comprising a transparent main body 4 (it can also be partially transparent and partially opaque), a transparent surface film 6 fixed to the main body 4 and comprising two faces opposite to each other with at least one relief 8 produced on each of the two faces and a transparent adhesive layer disposed between the main body and the surface film. The main body 4, the surface film 6 and the adhesive layer 14 are made of materials capable of refracting the light rays at least twice, a first time when the light rays reach one of the faces of the surface film and a second time when the light rays reach the other side of the surface film.

By transparency is meant the fact that a fraction of the light flux is able to pass through room 2. It is therefore a matter of the transmittance of visible light.

The surface film 6 is a film as described above. It includes one or more layers of plastic. The materials used are for example polyamides, polycarbonates or even polyurethane. For example, polyurethane is used as an inner layer and the outer layers forming the outer faces are made of polyamide. Polyamides have a refractive index between 1.53 and 1.59. Polycarbonates have a refractive index between 1.56 and 1.64. Polyurethane has a refractive index between 1.50 and 1.67. However, the value of the refractive index depends on certain parameters such as the density of the material through which the light passes. Furthermore, the refractive index of the polyamide may vary depending on the water saturation of the material. When the surface film 6 is produced in several layers of material, the surface layer or layers carrying the relief (s) are at least 150 micrometers thick for a surface film 6 with a thickness of between 0, 2 and 0.8 millimeters.

The surface film 6 comprises at least one relief 8, for example here three reliefs in the form of concentric circles. These patterns make it possible to obtain a depth effect which will be referred to below as a three-dimensional optical effect (lenticular effect). These patterns can be produced for example by stamping (or embossing) after extruding the film. This relief is visible in FIGS. 1A, 1C, 2A and 2C. The reliefs 8 are produced in the example illustrated on the two faces of the surface film 8, the face 10 opposite the main body 4 and the face 12 in contact with the main body 4. The number of reliefs 8 may obviously vary.

The main body 4 may for example be a bumper or a part of bumper located on the front face of the vehicle or of a hubcap. The surface film 6 can for example be placed on a solid surface in order to simulate the presence of a grid. The main body 2 can for example be made of polyamide, polycarbonate or else polymethyl methacrylate. It is therefore produced from a transparent plastic material which can be identical or different from that of the surface film 6. The main body 4 can then have an identical or different refractive index than that of the surface film.

In order to fix the surface film 6 to the main body 4, a layer of adhesive material 14 is added between the two. This adhesive layer 14 not only allows the fixing of the surface film 6 to the main body 4 but it also contributes to the preservation of an optimal optical effect. In fact, it is made of a material having a refractive index different from that of the surface film 6. The adhesive layer can for example be made of acrylic adhesive, a material having a refractive index equal to 1.49. It may for example be an adhesive of the Nitto® brand. In addition to the difference in refractive index, the adhesive layer is transparent. This makes it possible to obtain a transparent part 2 with an optimal optical effect.

More specifically, and as illustrated in FIG. 1C, part of the incident ray 16 is refracted for the first time when it passes from the air to the surface film 6. Part of the refracted ray 18 reaching the face 12 of the film of surface 6 is refracted a second time at the time of its passage in the adhesive layer 14. The resulting ray 20 continues its course then passes from the adhesive layer 14 to the main body 4 by undergoing a third refraction, as is the case on FIG. 1C (represented by arrow 22), as a function of the difference in refractive index between the material making up the adhesive layer 14 and the material of the main body 4.

This trajectory of the light rays makes it possible to obtain an optimal lenticular effect as shown in FIG. 1 B. In other words, the reliefs 8 present on the face 12 play a role in the refraction of the light rays, which allows to obtain an optimal optical effect with a transparent part.

FIGS. 2A to 2C illustrate a part 2 in another configuration, that is to say in the case where the light rays first reach the main body 4. It is therefore a case in point in which the surface film 6 will be placed on the internal face of a part, for example the unexposed face of a partially transparent decoration panel to simulate the effect of a grid.

The light rays pass through the adhesive layer 14 undergoing refraction during the passage between the main body 4 and the adhesive layer (always as a function of the difference between the refractive indices of the materials making up the adhesive layer 14 and the material of the main body 4 ) then they are refracted one during their passage from the adhesive layer 14 to the surface film 6 and then once again during its passage from the surface film 6 to the air. The refraction of the light rays is represented by the arrows 30, 32, 34 and 36.

This trajectory of light rays makes it possible to obtain an optimal three-dimensional optical effect as shown in FIG. 2B.

This scenario illustrates the importance of the transparency of part 2. In fact, an arrangement in which the light first passes through the main body and then the surface film cannot be envisaged with the incorporation solution according to the prior art because the impression made on the face would have reflected light, preventing it from passing through the surface film.

The invention is not limited to the embodiments presented and other embodiments will be apparent to those skilled in the art.

It is in particular possible to consider protecting the surface film when the latter is exposed and can be deteriorated due to the vagaries of the weather (rain, prolonged exposure to the sun, hail, ...). Such protection can be achieved by adding a layer of material above the surface film, for example a layer of transparent plastic or an adhesive layer. This additional transparent layer makes it possible to protect the surface film without degrading the optical properties of the part.

Nomenclature: motor vehicle part

4: main body: surface film: relief: face opposite to the main body: face in contact with the main body

14: adhesive layer: incident ray: refracted ray: ray crossing the adhesive: ray crossing the main body

30, 32, 34, 36: light rays in the alternative embodiment of the invention

Claims (8)

claims 1. Motor vehicle part (2) made of plastic material, characterized in that it comprises: - a main body (4) at least partially transparent, - a transparent surface film (6) comprising two faces (10, 12) opposite one another with at least one relief (8) produced on each of the two faces (10, 12), and - a transparent adhesive layer (14) disposed between the main body (4) and the surface film (6), the main body (4), the surface film (6) and the adhesive layer (14) being produced in materials capable of diffracting light rays at least twice, a first time when the light rays reach one of the faces (10, 12) of the surface film (6) and a second time when the light rays reach the other face (10, 12) of the surface film. 2. Part (2) according to claim 1, wherein the main body (4) is made of a material having a refractive index different from that of the surface film (6). 3. Piece (2) according to any one of the preceding claims, in which the adhesive layer (14) has a refractive index different from that of the main body (4). 4. Part (2) according to any one of the preceding claims, in which the adhesive layer (14) has a refractive index different from that of the surface film (6). 5. Piece (2) according to any one of the preceding claims, wherein the adhesive layer (14) comprises an acrylic adhesive. 6. Part (2) according to any one of the preceding claims, in which the relief (8) comprises bosses. 7. Part (2) according to any one of the preceding claims, wherein the main body (4) is made of polymethyl methacrylate. 8. Motor vehicle comprising a part (2) according to any one of the preceding claims.