Injection-molded plastic parts for lighting devices with functional surfaces
A composite component with a thermoplastic substrate and polyurethane or polyurea coating addresses manufacturing challenges by enabling complex shapes and improved optical/mechanical properties at reduced costs.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- VALEO VISION SA
- Filing Date
- 2021-12-17
- Publication Date
- 2026-05-25
AI Technical Summary
Existing lighting device components for motor vehicles face high manufacturing costs and geometric constraints due to high viscosity coefficients in thermoplastic materials, particularly in small-sized structures, and protective coatings like varnish are costly and limited in thickness and function.
A composite component comprising a substrate made of a first thermoplastic material and a coating made of polyurethane (PUR) or polyurea (PUA) is manufactured through reaction injection molding, where the second material cross-links with the first material at the interface, allowing for improved optical and mechanical properties while reducing costs.
The composite component achieves complex shapes with enhanced resistance to scratching and optical qualities like self-healing and microstructures, while maintaining cost-effectiveness by using lower viscosity materials.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to injection molded plastic parts, particularly in the field of lighting devices for motor vehicles.
Background Art
[0002] Conventionally, a lighting device for a motor vehicle has included a housing having an opening that forms a joint portion, and an outer lens that is fixed to the housing through the joint portion and closes the opening. The housing has conventionally been made of an injection molded opaque plastic material. The outer lens, which used to be commonly made of glass, has generally been made of an injection molded transparent plastic material, particularly polymethyl methacrylate (PMMA) or polycarbonate (PC), in recent years. These thermoplastic plastic materials (which are generally sold in the form of fine grains) are heated to a temperature exceeding the glass transition temperature in order to be injection molded thereafter. However, because these materials have a high viscosity coefficient, they require a high injection pressure. The high injection pressure requires an appropriate injection molding machine and may significantly increase the manufacturing cost. This high viscosity coefficient imposes geometric constraints on the part, particularly when the part to be manufactured has a small-sized structure (especially a light-scattering structure). In order to overcome this problem, it is known to form optical parts based on silicone. These parts often need to be attached to stronger parts. This solution is also very costly both from the perspective of material costs and from the perspective of its implementation.
[0003] It is also known to laminate a protective layer of varnish (transparent paint) on the outer surface of the outer lens. This varnish has an improved hardness in order to increase resistance to external attacks that are likely to cause scratches. This varnish has limitations inherent to varnishes, particularly in terms of thickness, (various) functions, implementation, etc. The varnish is also costly both from the perspective of raw materials and from the perspective of its implementation.
Summary of the Invention
Problems to be Solved by the Invention
[0004] The object of the present invention is to overcome at least one of the drawbacks of the prior art described above. More specifically, the object of the present invention is to produce plastic components for lighting devices having improved optical and mechanical properties, and to do so in an economical manner. [Means for solving the problem]
[0005] The subject of the present invention is a component for a vehicle lighting system, comprising a substrate made of a first thermoplastic material and a covering made of a second plastic material disposed on the substrate, wherein the second plastic material is made of polyurethane (PUR), polyurea (PUA), or a combination of PUR and PUA.
[0006] The components of a lighting device may have one or more of the following characteristics, either individually or in combination:
[0007] According to one advantageous embodiment of the present invention, the first and second materials have polar bonds between them at the interface between them. These polar bonds are the result of reaction injection molding of the two materials, i.e., the second material is injected after the first material in the same manufacturing process, although in two separate injections. Specifically, the second material cross-links with the polyol isocyanate through a chemical reaction while the first material is still warm to room temperature.
[0008] According to one advantageous embodiment of the present invention, the first thermoplastic material includes polymethyl methacrylate (PMMA), polycarbonate (PC), and a combination of PMMA and PC.
[0009] According to one advantageous embodiment of the present invention, the substrate forms a wall with an average thickness greater than the average thickness of the coating.
[0010] According to one advantageous embodiment of the present invention, the coating has an average thickness between 0.1 and 10 mm, preferably between 1 and 5 mm.
[0011] According to one advantageous embodiment of the present invention, the substrate and coating are transparent and each has a transmittance of at least 92% for visible light.
[0012] According to one advantageous embodiment of the present invention, the second material is made of PUA.
[0013] According to one advantageous embodiment of the present invention, the second material is made of PUR.
[0014] According to one advantageous embodiment of the present invention, the component is an outer lens for closing a lighting device.
[0015] According to one advantageous embodiment of the present invention, the coating forms the outer surface of the component which is self-healing by the application of a heat source to the coating.
[0016] According to one advantageous embodiment of the present invention, the structure of the second material includes arrangements and superpositions of short chains of approximately 100 to several thousand carbon atoms (typically between 100 and 8,000 carbon atoms). In other words, the second material exhibits oligomeric properties.
[0017] According to one advantageous embodiment of the present invention, the coating forms the inner surface of the component, which is provided with an optical microstructure. The meaning of the microstructure is 10 -3 The structure or geometry has main dimensions of less than or equal to a millimeter. For this purpose, the microstructure may have nanoscale dimensions. The microstructure can be optical, for example, dispersive. The microstructure can also provide hydrophobic properties.
[0018] A further subject of the present invention is a lighting system for an automatic vehicle equipped with the components according to the present disclosure.
[0019] The subject of the present invention is a method for manufacturing a component of a motor vehicle lighting device, comprising the steps of injecting a first thermoplastic material into a mold in a first geometry so as to form a substrate, and subsequently injecting a second plastic material into the mold in a second geometry so as to form a coating on the substrate while the first material has not yet cooled completely to ambient temperature, wherein the second plastic material consists of polyurethane PUR, polyurea PUA, or a combination of PU and PUA, particularly a combination of PUR and PUA.
[0020] The measures of the present invention are each advantageous in that they make it possible to manufacture components of lighting devices (particularly optical components) that have a complex shape while exhibiting respective special mechanical and / or optical qualities (such as resistance to scratching and / or fine structure). The manufacturing cost is also limited by the fact that the coating is thinner compared to the substrate made of a thermoplastic material that is cheaper per se.
Brief Description of the Drawings
[0021] [Figure 1] Cross-sectional view of the outer lens of a lighting device according to a first embodiment of the present invention. [Figure 2] Cross-sectional view of the outer lens of a lighting device according to a second embodiment of the present invention. [Figure 3] Schematic cross-sectional view of a plastic injection molding machine with a rotating mold, showing the injection of the first material according to the present invention. [Figure 4] Schematic cross-sectional view of a plastic injection molding machine with a rotating mold, corresponding to FIG. 3 and showing the injection of the second material according to the present invention.
Embodiments for Carrying Out the Invention
[0022] FIG. 1 is a schematic representation of the outer lens of a lighting device according to a first embodiment of the present invention.
[0023] The outer lens 2 comprises a transparent wall 4 and feet 6 for fixing to a lighting device housing (not shown). In this case, the wall 4 forms the left surface. The fixing feet 6 are integrally formed with the wall 4 at one edge of the wall 4. The wall 4 comprises a substrate 4.1 made of a first transparent plastic material of the thermoplastic class (e.g., polymethyl methacrylate PMMA, polycarbonate PC, or even a combination of PMMA and PC). The use of such materials for this type of application is well known in itself. The substrate 4.1 is manufactured by injecting the plastic material into a mold. The wall 4 further comprises a coating 4.2 that forms the outer surface of the outer lens 2 in this case. This coating has the function of forming a protective layer for the outer lens 2, i.e., protecting the outer lens 2 from external attacks (especially scratches). This coating 4.2 has self-healing properties (i.e., the ability to reduce or remove damage such as scratches) by the application of heat to raise its temperature. This property is known in itself and is commonly referred to in the term self-healing. For this purpose, coating 4.2 is made of a second plastic material based on polyurea PUA. PUA is the product of the polyaddition of aliphatic or aromatic isocyanates or isocyanate prepolymers to polyfunctional amines or mixtures of amines, specifically the bonding between isocyanates and various polyamines. It is commercially available from PANADUR (registered trademark) under the product name PANADUR CLEAR FAST. This product is a two-component product, namely a main component and a curing agent. The product is transparent and is commonly used as a "gel coat" type coating for composite materials consisting of a base material such as resin and carbon or glass fibers.
[0024] The inventors of the present invention have discovered the following. That is, for the purpose of forming a coating having protective properties for a substrate, by injecting a PUA-based plastic material together with a substrate (for example, a substrate as detailed above), varnishes that are expected to be more costly can be replaced. The protective properties include high hardness, which can be adjusted by the ratio between the components of the PUA-based plastic material and also by the self-healing ability. This property is due to the structure of the plastic material (typically, about 100 carbon atoms), that is, the arrangement and overlap of short chains. Scratches (for example, minute grooves formed by the movement of a sharp object on the coating) will separate these short chains in some overlapping layers. By applying an external heat source (for example, a hair dryer), when the temperature of the coating (typically reaching 60 to 90 °C) rises, these short chains can be rearranged by rearranging themselves so as to overlap each other.
[0025] PUA has a low viscosity coefficient (typically between 1.3 and 2 Pa·s at 20 °C, close to that of water), which is advantageous for implementation by injection. Co-injection means that the first and second plastic materials are injected at different times (preferably, into the same mold) during the same manufacturing process. This is because it enables the first plastic material injected first to solidify to some extent before the second plastic material is injected. Using the same mold does not rule out the possibility that the substrate obtained by the first (i.e., the first plastic material) injection is transferred into another cavity with a different geometry for the second (in this case, the second plastic material) injection.
[0026] It should be noted that in the context of the first embodiment, PUR can also be used as a substitute for PUA.
[0027] Figure 2 is a schematic representation of the outer lens of a lighting device according to the second embodiment of the present invention.
[0028] The reference numerals of the first embodiment are used to indicate corresponding or identical elements in the second embodiment, but these numerals are increased by 100. Furthermore, the descriptions of these elements given in the context of the first embodiment are referenced.
[0029] The outer lens 102 differs in essence from that of the first embodiment in the following respect: namely, the coating 104.2 of the wall 104 forms the inner surface of the wall and also forms a microstructure 104.3. It is advantageous that the microstructure 104.3 has optical properties, particularly light diffusion properties. The presence of a microstructure on the inner surface of the outer lens of a lighting device is known to those skilled in the art. In this case, the structure is obtained by a second plastic material that forms the coating 104.2 of a substrate 104.1 made of a first thermoplastic material such as polymethyl methacrylate (PMMA), polycarbonate (PC), or a combination of PMMA and PC. The second plastic material may be based on polyurethane (PUR) injected onto the first plastic material. Such plastic materials are commercially available from RUHL Puromer GmbH under the names puroclear 3351IT and 3098 / 4IT, particularly with the use of puronate 960 / 1. These materials are transparent, have a transmittance of over 92%, and a low viscosity coefficient of approximately 1 to 2.5 Pa·s at 25°C (i.e., very close to the viscosity coefficient of water). This plastic material is therefore particularly advantageous for injection molding for the purpose of forming microstructures 104.3.
[0030] The inventors of this invention have discovered that PUR can and is advantageous to use to form a coating by injection on a substrate made of a thermoplastic material with a considerably high viscosity coefficient in the molten state, which itself cannot create intricate structures such as optical microstructures. Injection molding of thermoplastic materials such as PMMA and PC presents problems when manufacturing long parts, as it is known to require high injection pressure. The high viscosity coefficient of the molten plastic material injected into the mold creates a flow resistance that increases with the injection length from the point of entry into the mold. This means that the injection pressure at the mold entrance (and therefore expected to be high) gradually decreases with distance to the furthest end of the material in the injection path. However, creating shapes with minute details requires applying a minimum amount of pressure to the injected material in order to completely fill these details, especially in the manufacture of microstructures. Therefore, a molding method by reaction injection molding of a substrate 104.1 made of a thermoplastic first plastic material and a coating 104.2 that forms a microstructure 104.3 made of a second plastic material (in this case, PUR) having a low viscosity coefficient and containing several components that react after injection is particularly advantageous.
[0031] It should be noted that, within the context of the second embodiment, PUA can be used instead of PUR.
[0032] It should be understood that the outer surface of a component can be formed by providing a first coating on a first surface of the substrate, and the inner surface of a component can be formed by providing a second coating on the opposite surface of the same substrate. Furthermore, each of the first and second coatings can conform to one of the coatings shown in Figures 1 and 2.
[0033] In general, and especially in the first and second embodiments described above, it is advantageous that the second plastic material is PUR, PUA, or a combination of PUR and PUA. This is essentially due to the low viscosity coefficient of these materials, which allows for injection even in thin layers without problems. The substrate made of the first plastic material constitutes a larger portion of the part (in this case, the outer lens). It can account for at least 70%, preferably at least 80%, of the mass of the part. The first plastic material is inexpensive, which allows for limiting manufacturing costs. PUR and PUA can also be transparent, and therefore have the advantage of enabling the manufacture of optical components such as the outer lens of the lighting device described above, or even various lenses.
[0034] Generally, the coating can have an average thickness of 0.5 mm (preferably 1 mm) or more and / or less than 10 mm (preferably 5 mm). The substrate is advantageous if it has an average thickness greater than the average thickness of the coating, and even more advantageous if it has an average thickness greater than three times the average thickness of the coating.
[0035] Figures 3 and 4 show embodiments of injection molding of the first and second plastic materials using a rotary mold.
[0036] Figure 3 is a schematic cross-sectional view of an injection molding machine with a rotary mold. The injection molding machine 8 comprises a first injection screw 8.1 for a first plastic material and a second injection screw 8.2 for a second plastic material. The rotary mold 10 comprises a fixed part 10.1 and a rotary movable part 10.2. The fixed part 10.1 is fixed to the injection molding machine 8 and has a first surface 10.1.1 and a second surface 10.1.2 which is different from the first surface 10.1.1. The movable part 10.2 similarly has a first surface 10.2.1 and a second surface 10.2.2. Unlike the fixed part 10.1 of the mold 10, the first surface 10.2.1 and the second surface 10.2.2 are identical. The first surface 10.1.1 of the fixed portion 10.1 and one of the first and second surfaces 10.2.1 and 10.2.2 of the movable portion 10.2 allow the movable portion 10.2 to form a first cavity and injection geometry of the first plastic material when pressed against the fixed portion 10.1, enabling the creation of a substrate 4.1 using the first injection screw 8.1 of the injection molding machine 8. Once the substrate 4.1 has been injected and cooled, the movable portion 10.2 of the mold translates along the axis 12 to pull out the substrate 4.1 remaining on the first surface 10.2.1 of the movable portion 10.2. Then, the movable portion 10.2 undergoes a rotation (in this case, about 180°) so that the substrate 4.1 faces the opposite side of the second surface 10.1.2 of the fixed portion 10.1 of the mold 10.
[0037] Figure 4 shows the injection molding machine and mold of Figure 3 at the stage in which the second plastic material is injected by the second injection screw 8.2. The components of the second plastic material can be mixed together in the injection screw before being injected into the mold 10. For this purpose, the movable part 10.2 of the mold 10 is moved closer to the fixed part 10.1 so that the second surface 10.2.2 of the movable part 10.2 that holds the substrate 4.1 enters the second part 10.1.2 of the fixed part 10.1 of the mold 10. This is so that the second cavity and injection geometry are defined by the second part 10.1.2 of the fixed part 10.1 and the substrate 4.1. The second plastic material can then be injected into it to form a coating 4.2. The coating 4.2 is shown with a deliberately exaggerated thickness for the purpose of clarity of representation. The first plastic material forming the substrate 4.1 is still hot when the second plastic material is injected. This is so that the two plastic materials undergo chemical bonding at their interface. This chemical bonding is achieved by covalent or polar bonding between the first and second plastic materials, without the presence of any adhesive.
[0038] Alternatively, the components of the second plastic material can be mixed together in a mixer attached to an injection molding machine. The second plastic material is then transferred into the mold via a nozzle.
[0039] The process described so far has been deliberately simplified for the purpose of illustrating the principle by which the components of a lighting device are manufactured using a rotary mold according to the present invention. However, it should be understood that it is possible to manufacture the components of the lighting device according to the present invention in other ways.
Claims
1. - A substrate made of the first thermoplastic material (4.1), - A covering (4.2) made of a second plastic material is placed on the substrate (4.1), In a component (2) of a lighting device for an automatic vehicle, The second plastic material consists of polyurethane (PUR), polyurea (PUA), or a combination of PUR and PUA. The coating (4.2) forms the outer surface of the component which is self-healing by the application of a heat source to the coating. The second plastic material exhibits oligomeric properties, and due to these oligomeric properties, when heat is applied to the second plastic material, it rearranges itself so that the short chains of oligomers separated by scratching overlap, and the number of carbon atoms in the short chains is between 100 and 8000, component (2).
2. The component (2) according to claim 1, wherein the first thermoplastic material and the second plastic material have polar bonds with each other at the interface between them.
3. The component (2) according to claim 1 or 2, wherein the first thermoplastic material includes polymethyl methacrylate (PMMA), polycarbonate (PC), and a combination of PMMA and PC.
4. The component (2) according to any one of claims 1 to 3, wherein the substrate (4.1) forms a wall (4) with an average thickness greater than the average thickness of the coating.
5. The component (2) according to any one of claims 1 to 4, wherein the coating (4.2) has an average thickness between 0.1 and 10 mm.
6. The component (2) according to any one of claims 1 to 5, wherein the substrate (4.1) and the coating (4.2) are transparent and each has a transmittance of at least 92% for visible light.
7. The part is an outer lens for closing the lighting device, part (2) according to claim 6.
8. - A step of injecting a first thermoplastic material into a mold (10) in a first geometric shape (10.1.1) to form a substrate (4.1), - Subsequently, while the first thermoplastic material has not yet cooled to ambient temperature, the second plastic material is injected into the mold (10) in a second geometric shape (10.1.2) to form a coating (4.2) on the substrate (4.1), A method for manufacturing a component (2) of a lighting device for an automatic vehicle, comprising: The second plastic material consists of polyurethane (PUR), polyurea (PUA), or a combination of PU and PUA. The coating (4.2) forms the outer surface of the component which is self-healing by the application of a heat source to the coating. The second plastic material exhibits oligomeric properties, and due to these oligomeric properties, when heat is applied to the second plastic material, it rearranges itself so that the short chains of oligomers separated by scratching overlap, and the number of carbon atoms in the short chains is between 100 and 8000, in a method.