Film structure and electronic device housing utilizing the same

An electronic device housing includes a substrate, a film structure, and a protective film. The film structure includes an adhesive film, a film stack, and a protective film. The adhesive film is deposited onto the substrate. The film stack is deposited onto the adhesive film alternating dielectric films and metal films. The metal films are non-continuous with a total thickness of the metal films at a predetermined value. The protective film is deposited onto an upper film of the film stack.

BACKGROUND

1. Technical Field

The disclosure relates to a film structure and an electronic device housing utilizing the same.

2. Description of the Related Art

Many electronic devices such as mobile phones employ a housing coated with a metal film to enhance appearance. The metal film typically exhibits high radio wave absorptivity. This feature decreases communication quality of the electronic devices, which largely depends on reliable throughput of radio wave transmission.

Therefore, it is desirable to provide a film structure and an electronic device housing utilizing the same which can overcome the described limitations.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the film structure and the electronic device housing are described in detail here with reference to the drawings.

FIG. 1is a schematic cross-section view of a sheet of an electronic device housing100, according to the disclosure. The electronic device housing100, such as a mobile phone housing, the sheet includes a substrate110, and a film structure120disposed thereon. Here as an example, the substrate110is transparent material such as glass or plastic.

The film structure120includes an adhesive film122, a film stack124, and a protective film126.

The adhesive film122is disposed on the substrate110. The adhesive film122is a non-conductive material and provides high adhesion. For example, the adhesive film122can be silicon dioxide film formed by physical vapor deposition (PVD).

The film stack124is disposed on the adhesive film122and adhered to the substrate110thereby. The film stack124alternates at least one metal film124aand at least one dielectric film124b. The metal film124ais a non-continuous film and may be Chromium (Cr), Aluminum (Al), or Silver (Ag). The dielectric film124bis non-conductive silicon dioxide film. Here, the metal film124aand the dielectric film124bare formed by PVD.

A metal film124aexhibits a maximum reflectivity at a requisite thickness. Disposition of metal film124ais non-continuously conducted prior to achieving the requisite thickness. As the thickness of the metal film124aincreases, the structure approaches continuity. Thus, to obtain maximum reflectivity and communication quality of the electronic device, the metal film is less than the requisite thickness. For example, an Al film stack achieves maximum light reflectivity, about 60%, at thickness of 30 nm (not including the alternative dielectric film124b). However, such a 30 nm Al film stack solely disposed on the substrate110is continuous. As a result, the electronic device will be shielded by the Al film, with communication quality thereof suffering. To solve the problem, as mentioned, the 30 nm Al film is separated into 6 layers and alternated with the dielectric layers. The layers of the Al film can have a similar or different thickness. However, the total thickness of the metal film124ais formed from 20 to 40 nm.

The protective film126is configured to protect the film stack124from oxidization, and can be non-conductive material such as silicon dioxide. However, if the top layer of the film stack is a dielectric film124b, the protective film126can be omitted and the dielectric film124bcan function as the protective film.

FIG. 2is a graph showing spectral characteristics of a first embodiment of an electronic device housing100. In this embodiment, the film stack124includes six metal films124aand five dielectric films124b. Here, each metal film124ais Cr film, and has a thickness of 5 nm.

Table 1 presents a relationship of refractive index (n) and extinction coefficient (k) of the Cr film from different wavelengths of visible light.

If the metal film124ais Cr, the n of the electronic device housing100is approximately 60%. Consequently, the mirror effect increases with n.

InFIG. 3, spectral characteristics of a second embodiment of the electronic device housing100are shown, differing from the first embodiment in that metal film124ais Al.

Table 2 presents a relationship of the n and the k of the Al film from different wavelengths of visible light.

With metal film124aof Al, the n of the electronic device housing100exceeds 80%. As before, the mirror effect increases with n.

InFIG. 4, spectral characteristics of a third embodiment of the electronic device housing100are shown, differing from the first embodiment in that metal film124ais Ag.

Table 3 presents a relationship of the n and the k of the Ag film from different wavelengths of visible light.

If the metal film124ais Ag film, the n of the electronic device housing100is from 50% to 90%. As before, the mirror effect increases with n.

It is noted that in the film stack124, metal film and alternating dielectric film, each forms an island structure (rough and uneven in surface) so that signals from the electronic device housing100pass therethrough, providing optimum communication without shielding.