Method for producing transparent or semi-transparent components

Abstract

A method is disclosed for producing a component formed by two layers (30, 40) of different, transparent or semi-transparent materials, wherein the component is molded in a mold (10) by over-molding two layers. One layer (40) is constituted by a polymer having structural characteristics and being resistant to impact, fracture or chipping, for example PC, and the other layer (30) is constituted by a polymer characterized by high scratch resistance, such as PMMA.

Claims

1. Method for producing a molded component, the component being a lens or a sunroof or a windscreen for a vehicle, and formed by two layers (30, 40) of different, transparent or semi-transparent materials, with the steps of providing one layer consisting of a polymer having structural characteristics and being resistant to impact, fracture or chipping, and providing another layer consisting of a polymer characterized by high scratch resistance; over-molding the two layers in a mold thereby molding the final component.

2. Method according to claim 1, wherein the component is molded with a sequence which first provides for the molding of said one layer and then of said other layer, or vice versa.

3. Method according to claim 2, wherein one layer is molded in a press and the other layer is molded in a different press by over-molding it to the said one layer.

4. Method according to claim 1, wherein the two layers are in contact along a single contact surface.

5. Method according to claim 1, wherein the layer injected first forms a concave solid, and the layer injected second covers all the concave or convex surface of the solid.

6. Method according to claim 1, wherein the layer injected first forms a concave solid, and the layer injected second partially covers the concave or convex surface of the solid.

7. Method according to claim 6, wherein the layer that partially covers the concave or convex surface of the solid is a flat or slightly curved layer.

8. Method according to claim 6, wherein the layer that partially covers the concave or convex surface of the solid is placed at the center of the solid.

9. Component produced by the method of any one of the preceding claims.

10. Lens or sunroof or windscreen for a vehicle, comprising or consisting of a two-layer structure made of transparent or semi-transparent materials, the structure comprising the superposition of a layer molded with a polymer having structural characteristics and being resistant to impact, fracture or chipping, and a layer molded with a polymer characterized by high scratch resistance.

11. Lens or sunroof or windscreen for a vehicle as in claim 10, wherein the polymer having structural characteristics and being resistant to impact, fracture or chipping is polycarbonate.

12. Lens or sunroof or windscreen for a vehicle as in claim 10, wherein the polymer characterized by high scratch resistance is polymethylmethacrylate.

13. Method according to claim 1, wherein the polymer characterized by high scratch resistance is polymethylmethacrylate.

14. Method according to claim 1, wherein the polymer having structural characteristics is polycarbonate.

Description

(1) The advantages of the invention will be made even clearer by the following description of a preferred embodiment of the injection system for performing the method, in which reference is made to the accompanying drawing wherein

(2) FIG. 1 shows a production method of the known type;

(3) FIGS. 2-4 show variants of a production system according to the invention.

(4) In the figures same reference numerals indicate same elements, which are sometimes without references not to crowd the drawing.

(5) The process according to the invention may be carried out, for example, on a known press of the stack-mould type with rotating central table, thanks to which it is possible to have two next molding stations in the same injection molding machine.

(6) FIG. 2 shows a mould 10 in which a cavity 16 adapted to be filled by plastic material injected into the mould by known injectors 20, is formed.

(7) Closed the mould, by successive injections of material a component can be produced with two layers 30, 40 of different materials, one over-molded to the other. The injectors 20 shown here are used for the injection of the generic second layer.

(8) The inner layer 40 is constituted of polymer with structural characteristics such as impact, fracture resistance and resistance to chipping, for example PC.

(9) The outer layer 30 is instead made of material characterized by high aesthetic quality and scratch resistance, such as PMMA.

(10) It can be seen, then, that in this way the final two-layer component has an outer visible surface 32 with aesthetic and anti-scratch characteristics, but has however sufficient mechanical resistance thanks to the underlying structural layer 40.

(11) The molding sequence can indifferently provide for the molding of the first structural part 40 and then of the scratch-resistant part 30, or vice versa.

(12) E.g. in FIG. 2 the part 30 is injected first, while in FIG. 3 the part 40 first.

(13) In FIGS. 2 and 3, the overlap of the two materials involves all the volume of the final component, which in fact consists in the overlapping of two scaled elements. In particular, the part 40 forms a solid concave whose convex surface is completely covered by the part 30.

(14) By the method of the invention one may also achieve that the final component comprises two layers of material only on an area that, in use, is visible from the outside, see FIG. 4. it is sufficient to properly design the cavity 16 of the mould.

(15) In particular in FIG. 4 it can be observed that the molded component is two-layered and always has a part 52, e.g. the central one, which constitutes the visible outer surface, with aesthetic and anti-scratch characteristics, and a structural layer 50. However in this case the part 52 only partially covers the structural layer or part 50, relatively to a surface which during the final use will remain on sight, as e.g. the outer surface of a headlight. Thus an uncovered area 54 of the component 50 remains. In other words, the solid formed by the concave part 50 has its own convex surface only partly covered by the part 52.

(16) The area has 54 different utilities. E.g. if the molded component is a lens of the vehicle headlight, the transparent or semi-transparent part is that the frontal one visible from the outside (of the vehicle), i.e. the layer 30 or 52. The contour or no-overlap areas 54 between the two layers often have the purpose of fixing the lens to the body (case of FIG. 4), and are usually opaque (e.g. black) and do not require anti-scratch treatment. There may, however, be transparent or semi-transparent border areas, protected by the vehicle body and for this not in need of anti-scratch coating. For roofs or rear windows the same concept holds.

(17) Even for the variant of FIG. 4 the molding sequence may be reversed, i.e. the part 52 may be molded first and then the part 50 is over-injected thereto. In this case, the part 52 molded first forms a concave solid having a concave surface. On all such concave surface the part 50 is over-injected.

(18) Another variant provides that the lens is produced also with a sequence of different phases, e.g.: molding a layer on a first press, e.g. the layer 30; extracting the layer from the first press and inserting it in a second press (technically an insert); in the second press, molding a second layer, e.g. the layer 50, by over-molding it on the layer previously inserted in the second press to obtain the overall lens.

(19) In particular, a two-layer lens (made of PC+PMMA) can then be produced by: molding the PMMA on a first press; inserting the layer of PMMA thus obtained in a second press (as an insert); over-molding a layer made of PC on the layer made of PMMA.

(20) All of the advantageous variants described above are also applicable to this last method embodiment that uses two different presses to produce one layer at a time.