WO2021127691A1

WO2021127691A1 - Engineered surface finish of plastic part having a microbead surface coating

Info

Publication number: WO2021127691A1
Application number: PCT/US2020/070909
Authority: WO
Inventors: Alfredo Castillo; Irina KOGAN-MICHEDO; Eugene LIAO; Chih Kai Hu
Original assignee: Google Llc
Priority date: 2019-12-17
Filing date: 2020-12-14
Publication date: 2021-06-24

Abstract

A method of making a housing of an electronic device includes fabricating a polymer device housing for the electronic device though an injection molding process and applying a layer of microspheres to a surface of the polymer device housing, where applying the layer of microspheres to the surface includes applying the microspheres, such that portions of surfaces of the microspheres are exposed and uncovered by polymer material on a surface of the polymer device housing.

Description

ENGINEERED SURFACE FINISH OF PLASTIC PART HAVING A MICROBEAD SURFACE COATING

BACKGROUND

[0001] The look, feel, and function of the housing of a portable electronic device is of critical importance to the overall user experience and satisfaction with the device. Many users prefer devices with housing having hard, highly -poll shed surfaces, which give the impression of the device being a “high-end” device having a smooth, cool, polished finish. However, housings constructed of metal and/or glass may be relatively expensive and/or difficult to manufacture compared to injection molded (e.g., plastic) parts.

[0002] Therefore, there exists a need for housings of portable electronic devices that can be manufactured relatively inexpensively but that also have a satisfying appearance and function for the user.

SUMMARY

[0003] This disclosure describes engineered plastic parts having a surface finish that includes a layer of microbeads. The layer of microbead can impart a desired look and feel to the surface of the part, while still allowing efficient, low-cost production techniques to be used to make the parts.

[0004] In a general aspect, a method of making a housing of an electronic device includes fabricating a polymer device housing for the electronic device though an injection molding process and applying a layer of microspheres to a surface of the polymer device housing, where applying the layer of microspheres to the surface includes applying the microspheres, such that portions of surfaces of the microspheres are exposed and uncovered by polymer material on a surface of the polymer device housing.

[0005] Implementations can include one or more of the following features, in any combination with each other.

[0006] For example, a median diameter of the microspheres in the layer can be less than 50 microns. [0007] A standard deviation of diameters of the microspheres in the layer is less than 20% of a median diameter of the microspheres.

[0008] The microspheres can include glass.

[0009] The layer of microspheres can include a monolayer of microspheres.

[0010] Applying the layer of microspheres to the surface can include applying the microspheres using an in-mold decoration process.

[0011] The in-mold decoration process can include placing an intermediate layer to which the microspheres are adhered in a cavity of a mold along a wall of the mold, injecting the polymer material into the cavity of the mold, curing the injected polymer material with the microspheres adhered to the surface and to the intermediate layer, and releasing the microspheres from the intermediate layer.

[0012] The intermediate layer can include a release material.

[0013] The microspheres can be partially embedded in the intermediate layer when the polymer material is injected into the cavity of the mold.

[0014] The surface can be polished after curing the injected polymer material.

[0015] Applying the layer of microspheres to the surface can include applying the microspheres using an out mold decoration process.

[0016] The out mold decoration process can include applying an adhesive layer to the surface of the polymer device housing, applying the microspheres to the adhesive layer, and curing the adhesive layer to bond the microspheres to the surface.

[0017] Applying the microsphere to the adhesive layer can include applying a film carrying the microspheres to the adhesive layer, and releasing the carrier film form the microspheres after the adhesive layer has been cured.

[0018] In another general aspect, a housing of an electronic device includes an injection- molded polymer device housing, and a layer of microspheres on a surface of the injection- molded polymer device housing, where portions of surfaces of the microspheres are exposed and uncovered by polymer material on the surface of the polymer device housing.

[0019] Implementations can include one or more of the following features, in any combination with each other. [0020] For example, a median diameter of the microspheres in the layer can be less than 50 microns.

[0021] A standard deviation of diameters of the microspheres in the layer is less than 20% of a median diameter of the microspheres.

[0022] The microspheres can include glass.

[0023] The layer of microspheres can include a monolayer of microspheres.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, serve to further illustrate implementations set forth in this disclosure.

[0025] FIG. l is a front perspective view of an electronic device.

[0026] FIG. 2 is a rear perspective view of the electronic device according to FIG. 1.

[0027] FIG. 3 is a schematic side view of a fabricated part having an engineered surface finish that includes a layer of microspheres.

[0028] FIG. 4 is a schematic side view of an apparatus that can be used to apply a layer of microspheres to a surface of a fabricated part.

[0029] FIG. 5 is an enlarged view of microspheres partially embedded in intermediate layer.

[0030] FIGS. 6-8 illustrate an out molding process of forming a finished fabricated part having a bulk substrate composed of one material (e.g., a polymer material) and having a surface embedded with microspheres composed of another material (e.g., glass).

[0031] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various implementations disclosed herein.

[0032] The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing the specific details that are pertinent to understanding the various implementations and not obscuring the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. DETAILED DESCRIPTION

[0033] In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the implementations disclosed herein. However, it will be apparent to one skilled in the art that these implementations can be practiced without these specific details. In some instances, structures and devices are shown in block diagram form for the sake of conciseness.

[0034] The implementations described herein are illustrative of products and processes of manufacturing products that can be relatively inexpensive to manufacture but also have the appearance, feel, and mechanical properties of more expensive, “higher-end” products. In particular, plastic parts, for example, plastic parts made through an injection molding manufacturing process, can have surface finishes that include a layer of microspheres that include non-plastic (e.g., glass, ceramic, metal, etc.) material, such that the surface of the part can have the look, feel, and mechanical properties of the material of which the microspheres are composed.

[0035] An electronic device 100 including a housing is illustrated in FIGS. 1 and 2. FIG. 1 includes a reference coordinate system that is referred to below, indicating left and right sides of the device 100 (from a user’s perspective when holding the device), top and bottom sides (or ends) (the top being the side generally away from the ground during normal use, and the bottom being the side generally toward the ground during normal use), and front and rear sides (the front being the side facing a user during normal use, and the rear side being the side facing away from a user during normal use).

[0036] The electronic device 100 may be any portable electronic device that includes a display, and may, for example, be a cellular phone, a smart phone, a tablet, an internet device, a music player, or any other device that includes a display that can advantageously employ the housing disclosed herein. Additionally, the mobile smartphone features of the communication device 100 illustrated herein are provided by way of example, and are in no way intended to be limiting, nor essential to the housing described herein.

[0037] The electronic display device 100 includes a display 102 Speaker port 108 and a microphone port 110 openings allowing unobstructed access to a device speaker and a microphone, respectively, that can be located at opposite ends of a display window 104 through which a user can view a display carried in the electronic device 100 The illustrated device 100 may include a forward-facing camera 112 and an electrical connector port 114 for accessing circuitry within the housing of the device. For example, the port 114 may accommodate a connector, such as a male connector, and may include, for example, a commercially available connector, such as a universal serial bus (USB) connector, a mini USB, a micro USB, a USB- C, or other any other suitable connector.

[0038] The electronic display device 100 includes a rear housing 200 (FIG. 2). The rear housing 200 may include a rear microphone port 202, a rear speaker port 204 and a rear facing camera 206 similar to those found on the front of the device. Also illustrated in FIG. 2 is a removable card access door 210 for insertion and removal of electronic cards, such as a memory card, a subscriber identity module (SIM), or any other removable card that can be advantageously employed in the electronic device.

[0039] The rear housing 200 may be manufactured from a composite material, such as an injection-molded plastic formed during a molding process. The composite material may include a sheet formed to the intended three-dimensional shape of the rear housing 200, to provide a curved surface that is pleasant to hold and fitting comfortably in a hand when held. In some implementations, this shape may have a curvature in both the left-to-right side direction as well as a top-to-bottom end direction, where the curvature includes the entire right -to-left direction and/or the entire top-to-bottom direction. In some implementations, this shape may have a flat portion in one or both directions, where curved portions extend only near the edge regions.

[0040] FIG. 3 is a schematic side view of a fabricated part 300 having an engineered surface finish that includes a layer of microspheres 306. The fabricated part 300 can include a polymer material (e.g., a plastic material) that can be formed into its desired shape, for example, through a molding process. The fabricated part 300 can include a substrate layer 302 of material (e.g., polymer material) and the surface layer of microspheres 306, where, in some implementations, the microspheres 306 can be integrated with the substrate layer 302 by an adhesive or bonding layer 304.

[0041] The microspheres 306 in the surface layer are generally spherical is shape and have a median diameter of less than 100 microns. In some implementations, the median diameter of the microspheres is less than 50 microns. In some implementations, the median diameter of the microspheres is less than 25 microns. In some implementations, the median diameter of the microspheres is less than 15 microns. In some implementations, the median diameter of the microspheres is less than 10 microns. In some implementations, the standard deviation of the diameters of the microspheres 306 in the surface layer is less than 10% of the median diameter. In some implementations, the standard deviation of the diameters of the microspheres 306 in the surface layer is less than 20% of the median diameter.

[0042] The microspheres 306 can be composed of various materials, for example, glass, metal, etc. Glass microspheres 306 in the surface layer can be solid or hollow, or the surface layer of microspheres 306 can include both solid and hollow microspheres. The glass used in the glass microspheres 306 can include soda lime glass, borosilicate glass, barium titanate glass, etc. Neighboring microspheres 306 can touch each other or can be separated from each other by small gaps due to the material 304 to which they adhere, bond, or are embedded. In some implementations, a monolayer of microspheres 306 can be included in the surface layer of the fabricated part 300, and in some implementations at least some microspheres 306 may be stacked on top of each other, such that more than a single monolayer of microspheres 306 exists on the surface layer of the fabricated part 300.

[0043] With a surface layer of microspheres 306, the material properties of the fabricated part 300 perceived by a user can be determined by the material properties of the thin surface layer of microspheres 306 rather than the bulk material properties of the substrate layer 302. For example, the hardness, smoothness, and reflectivity perceived a user of the fabricated part can be determined by the material properties of the microsphere 306 surface layer. Thus, by applying a surface layer of glass microspheres 306 to a substrate 302, the user may perceive the fabricated part 300 to have the hardness, smoothness, and reflectivity that one usually associates with a solid glass fabricated part, even though only the surface layer includes glass, while the substrate can be made of less expensive materials and can be formed using inexpensive mass production processes (e.g., injection molding processes).

[0044] In addition, the thermal inertia of the glass in the surface layer of microspheres 306 can be higher than that of typical plastics used to form fabricated parts, where the thermal inertia of a material is defined as the square root of the product of the materiaTs thermal conductivity, density, and specific heat capacity, and parameterizes the perception of a user’s experience of the temperature of a material. Because of the higher thermal inertia of glass microspheres 306 compared to polymers typically used to fabricate housings of consumer electronic devices, a user may experience a surface coated with glass microspheres 306 as feeling cooler to the touch than a polymer surface that has the same temperature as the glass microsphere 306 surface layer. [0045] The microspheres 306 can be applied to the surface layer of the fabricated part 300 in a number of different ways, for example, an in-mold decoration process or an out-mold decoration process.

[0046] FIG. 4 is a schematic side view of an apparatus 400 that can be used to apply a layer of microspheres to a surface of a fabricated part. The apparatus 400 can include a multi -part mold that includes parts 402 and 404, which define a shape of the finished fabricated part. Material to form the bulk of the finished fabricated part can be introduced to an interior cavity 406 defined by the mold parts though at least one inlet 408. For example, flowing polymer material can be introduced into the cavity 406 through the inlet to fill the cavity and then can be cured into a solid form defined by the dimensions of the mold by the application of, for example, heat and/or pressure and/or predetermined wavelengths of light to the polymer material. After the material in the cavity is cured, the part can be released from the mold and then finished (e.g., coated, polished, etc.).

[0047] A layer of microspheres 410 can be applied to a surface of the polymer material in the cavity through in in-mold decoration process to form a microsphere surface layer on the finished fabricated part that is formed by the mold. For example, in one implementation, an intermediate layer 412 between the microspheres 410 and a wall of the mold can hold the microspheres 410 at the surface of the polymer material while the polymer material is injected into the cavity 406 and while the polymer material cures. The intermediate layer 412 can have a lower adhesion to the microspheres 410 than the cured polymer material does, so that when the finished fabricated part is removed from the mold, it includes a surface layer of microspheres 410. Although the microspheres 410 may be partially embedded in the cured polymer material, a portion of the microspheres 410 may extend away from the cured polymer material, so that material properties of the surface of the finished fabricated part are defined by the material properties of the microspheres 410.

[0048] In some implementations, the intermediate layer 412 can include a release material (e.g., a wax) that is applied to the inside surface of the mold part 402, and then the microspheres 410 can be applied to the release material, which can temporarily hold the microspheres 410 in place while the polymer material is injected into the mold cavity 406 and cured in place. The microspheres 410 can be, for example, sprayed onto the release material. After the polymer material is cured, the stronger adhesion of the microspheres 410 to the cured polymer material than to the release material allows the microspheres 410 to be transferred from the release material to the surface of the injection molded part. [0049] FIG. 5 is an enlarged view of microspheres 410 partially embedded in intermediate layer 412. As seen in FIG. 5, a portion of the microspheres 410 can be partially embedded in the intermediate layer 412, such that the polymer material injected into the mold cavity 406 does not cover the surfaces of the microspheres 410 that are embedded in the intermediate layer 412. Then, when the microspheres 410 are bonded to the cured polymer material and released from the intermediate layer 412, the surfaces of the microspheres 410 that were embedded in the intermediate layer can form the surface layer of the fabricated part. The surfaces of the microspheres 410 can be further exposed by physically and/or chemically polishing the surface of the fabricated part after it is removed from the mold cavity 406 to remove cured polymer material from the surface of the microspheres 410 and from gaps between the microspheres 410.

[0050] In another implementation, the intermediate layer 412 can include a carrier film to which the microspheres 410 can be applied before the carrier film is placed inside the mold cavity 406, and then polymer material can be injected into the mold cavity. The carrier film can include, for example, a flexible substrate, such as, for example, polyethylene terephthalate (PET), poly(methyl methacrylate) (PMMA), polycarbonate (PC), polybutylene terephthalate (PBT), polypropylene (PP), polystyrene (PS), or combinations thereof. The microspheres 410 can be, for example, printed onto the carrier film of the intermediate layer 412, and then the carrier film can be placed inside the mold cavity where, though the in-mold decoration process, the microspheres 410 become integrated into the surface of the finished fabricated part produced in the molding process.

[0051] FIGS. 6-8 illustrate an out molding process of forming a finished fabricated part having a bulk substrate composed of one material (e.g., a polymer material) and having a surface embedded with microspheres composed of another material (e.g., glass).

[0052] As shown in FIG. 6, a cured substrate 600 of the fabricated part can have been fabricated by an earlier process, for example, by an injection molding process, and, after the fabrication of the substrate, microspheres 604 can be applied to a surface of the substrate 600. The microspheres 604 can be carried on a carrier film 606, as described above, and an adhesive layer 602 can be applied to a surface of the substrate 600, where the adhesive layer is applied to receive, and bond to, the microspheres 604. The adhesive layer 602 can include, for example, an epoxy material, an acrylic material, or other materials. The curing of the material in the adhesive layer can be controlled with a variety of techniques, including, for example, the application of heat, pressure, or certain wavelengths of light to the material. [0053] After application of the adhesive layer 602, as shown in FIG. 7, the film 606 carrying the microspheres 604 can be brought into contact with the adhesive layer 602, and then the microspheres 604 can be bonded to the adhesive layer 602. The curing of the adhesive layer to bond the microspheres 604 to the adhesive layer 602 can occur through the application of, for example, pressure (e.g., through a vacuum bagging process), heat, or curing with ultraviolet (UV) light.

[0054] As shown in FIG. 8, once the microspheres 604 have been bonded to the adhesive layer 602, the carrier film 606 can be released, and removed, from the microspheres 604, so that the microspheres 604 form the surface of the finished part. The effect of the material properties of the microspheres 604 on the surface of the finished fabricated part can be enhanced by physically and/or chemically polishing the surface of the finished part to expose additional surface area of the microspheres 604 on the surface of the finished fabricated part.

Claims

WHAT IS CLAIMED IS:

1. A method of making a housing of an electronic device, the method comprising: fabricating a polymer device housing for the electronic device though an injection molding process; and applying a layer of microspheres to a surface of the polymer device housing, wherein applying the layer of microspheres to the surface includes applying the microspheres, such that portions of surfaces of the microspheres are exposed and uncovered by polymer material on a surface of the polymer device housing.

2. The method of claim 1, wherein a median diameter of the microspheres in the layer is less than 50 microns.

3. The method of any of the preceding claims, wherein a standard deviation of diameters of the microspheres in the layer is less than 20% of a median diameter of the microspheres.

4. The method of any of the preceding claims, wherein the microspheres include glass.

5. The method of any of the preceding claims, wherein the layer of microspheres includes a monolayer of microspheres.

6. The method of any of the preceding claims, wherein applying the layer of microspheres to the surface includes applying the microspheres using an in-mold decoration process.

7. The method of claim 6, wherein the in-mold decoration process includes: placing an intermediate layer to which the microspheres are adhered in a cavity of a mold along a wall of the mold; injecting a polymer material into the cavity of the mold; curing the injected polymer material with the microspheres adhered to the surface and to the intermediate layer; and releasing the microspheres from the intermediate layer.

8. The method of claim 7, wherein the intermediate layer includes a release material.

9. The method of any of claims 7 or 8, wherein the microspheres are partially embedded in the intermediate layer when the polymer material is injected into the cavity of the mold.

10. The method of any of claims 7 - 9, further comprising polishing the surface after curing the injected polymer material.

11. The method of any of claims 1 - 5, wherein applying the layer of microspheres to the surface includes applying the microspheres using an out mold decoration process.

12. The method of claim 11, wherein the out mold decoration process includes: applying an adhesive layer to the surface of the polymer device housing; applying the microspheres to the adhesive layer; and curing the adhesive layer to bond the microspheres to the surface.

13. The method of claim 12, wherein applying the microsphere to the adhesive layer includes applying a carrier film carrying the microspheres to the adhesive layer; and releasing the carrier film form the microspheres after the adhesive layer has been cured.

14. A housing of an electronic device comprising: an injection-molded polymer device housing; and a layer of microspheres on a surface of the injection-molded polymer device housing, wherein portions of surfaces of the microspheres are exposed and uncovered by polymer material on the surface of the polymer device housing.

15. The housing of claim 14, wherein a median diameter of the microspheres in the layer is less than 50 microns.

16. The housing of any of claims 14 - 15, wherein a standard deviation of diameters of the microspheres in the layer is less than 20% of a median diameter of the microspheres.

17. The housing of any of claims 14 - 15, wherein the microspheres include glass.

18. The housing of any of claims 14 - 15, wherein the layer of microspheres includes a monolayer of microspheres.