Patent Publication Number: US-2010129624-A1

Title: Multi-layer film structure with medium layer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to commonly-assigned co-pending applications entitled, “MULTI-LAYER FILM AND ELECTRONIC DEVICE SHELL HAVING SAME,” (Atty. Docket No. US24658), and “MULTI-LAYER FILM AND ELECTRONIC DEVICE SHELL WITH SAME,” (Atty. Docket No. US24274). The above-identified applications are filed simultaneously with the present application. The disclosures of the above identified applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to multi-layer film structures, and particularly, to a colored multi-layer film structure. 
     2. Description of Related Art 
     Colored layer structures are used on shells of electronic devices such as mobile phones. Currently, the coloration of such shells is usually produced by painting. However, many paints are not environmentally friendly. For example, some paints or by-products thereof can be harmful to humans. Furthermore, many painted surfaces are not wear-resistant and are easily scratched. 
     What is needed, therefore, is a film structure which can overcome the above shortcomings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present multi-layer film structure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present multi-layer film structure. Moreover, in the drawings, all the views are schematic, and like reference numerals designate corresponding parts throughout the views. 
         FIG. 1  is a cross-sectional view of a multi-layer film structure in accordance with a first embodiment. 
         FIG. 2  is a cross-sectional view of a multi-layer film structure in accordance with a second embodiment. 
         FIG. 3  is a cross-sectional view of a shell of an electronic device in accordance with a third embodiment, the shell being an application environment of a multi-layer film structure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Various embodiments of the present multi-layer film structure will now be described in detail below and with reference to the drawings. 
     Referring to  FIG. 1 , an exemplary multi-layer film structure in accordance with a first embodiment is shown. The multi-layer film structure includes a multi-layer film  100  and a substrate  110 . The multi-layer film  100  includes in sequence an inmost layer  120 , a medium layer  130 , a reflective-transmissive layer  140  and an outmost layer  150 . 
     The inmost layer  120  is configured (i.e. structured and/or arranged) to cling (adhere) to the substrate  110 . The substrate  110  can be made of glass, plastic, metal, or ceramic. The substrate  110  can have a wide range of thicknesses, depending on the particular application. For example, the thickness may be in a range of from two microns to more than two centimeters. The inmost layer  120  is metallic, and a thickness thereof is in a range of from 0.3 nanometers (nm) to 10 nm. In the present embodiment, the inmost layer  120  contains chromium, and a thickness of the inmost layer  120  is approximately 0.5 nm. Because the thickness of the inmost layer  120  is slight, little light is reflected by the inmost layer  120 . 
     The medium layer  130  is adjacent to the inmost layer  120 . The medium layer can be formed on the inmost layer  120  by sputtering or chemical vapor deposition. The medium layer  130  is transparent, and contains a material selected from a group consisting of silicon dioxide, titanium oxide, niobium oxide, aluminum oxide and magnesium fluoride. In the present embodiment, the medium layer  130  contains silicon dioxide. A thickness of the medium layer  130  can be in a range of from 50 nm to 1000 nm; for example, 131 nm, 188 nm, 206 nm, 431 nm or 518 nm. The medium layer  130  is capable of controlling a color appearance of the entire multi-layer film  100 , by way of variation of the thickness of the medium layer  130 . The principle is explained below. 
     The reflective-transmissive layer  140  is formed on the medium layer  130 . The reflective-transmissive layer  140  is metallic. In the present embodiment, the reflective-transmissive layer  140  contains aluminum, and the reflective-transmissive layer  140  can be formed on the medium layer  130  by evaporation. A thickness of the reflective-transmissive layer  140  can be in a range of from 20 nm to 200 nm. The reflective-transmissive layer  140  reflects a portion of incident light, and allows another portion of the incident light to transmit therethrough. The portion of incident light reflected is designated as a first reflected light L 1 , and may for example be visible light which includes red, orange, yellow, green, blue, indigo and violet lightwaves. 
     The outmost layer  150  is formed on the reflective-transmissive layer  140 . The outmost layer  150  is metallic, and thus is wear-resistant. Depending on the type of metal used, the outmost layer  150  may also be corrosion-resistant. In the present embodiment, the outmost layer  150  contains chromium, and the outmost layer  150  can be formed on the reflective-transmissive layer  140  by liquid phase deposition or physical vapor deposition. A thickness of the outmost layer  150  can be in a range of from 1 nm to 30 nm. Because the thickness is slight, little light is reflected by the outmost layer  150 . 
     The substrate  110  has a thickness greater than that of the entire multi-layer film  100 . Accordingly, light transmitted through the multi-layer film  100  can be reflected by the substrate  110 . Such reflected light is designated as a second reflected light L 2 . The medium layer  130  is located between the substrate  110  and the reflective-transmissive layer  140 , and thus is capable of controlling a difference between the light path of the first reflected light L 1  and the light path of the second reflected light L 2 . Thereby, the second reflected light L 2  can interfere with the first reflected light L 1  in a desired manner. 
     When the light path difference between the first reflected light L 1  and the second reflected light L 2  is an even multiple of half of a central wavelength of a particular color lightwave of the visible light, that color lightwave is enhanced. Under this condition, the multi-layer film  100  (and also the entire multi-layer film structure) would appear to have a color substantially that of the most enhanced color lightwave. In one example, among the color lightwaves of visible light, i.e., red, orange, yellow, green, blue, indigo and violet, two of these color lightwaves may be enhanced. For instance, red and green lightwaves may both be enhanced. In such example, the multi-layer film  100  would appear to have a color comprised of a mixture of red and green; i.e., yellow. If the red lightwaves are enhanced more than the green lightwaves, the color has a tinge of red in it. If the green lightwaves are enhanced more than the red lightwaves, the color has a tinge of green in it. 
     Other more particular examples are as follows. When the thickness of the medium layer  130  is in a range of from 121 nm to 141 nm, for example, 131 nm, the color appearance of the multi-layer  100  is substantially blue. When the thickness of the medium layer  130  is in a range of from 177 nm to 195 nm, for example, 188 nm, the color appearance of the multi-layer  100  is substantially yellow. When the thickness of the medium layer  130  is in a range of from 196 nm to 226 nm, for example, 206 nm, the color appearance of the multi-layer  100  is substantially orange. When the thickness of the medium layer  130  is in a range of from 421 nm to 441 nm, for example, 431 nm, the color appearance of the multi-layer  100  is substantially violet (or violet). When the thickness of the medium layer  130  is in a range of from 514 nm to 534 nm, for example, 518 nm, the color appearance of the multi-layer  100  is substantially green. 
     Referring to  FIG. 2 , an exemplary multi-layer film structure in accordance with a second embodiment is shown. The multi-layer film structure is essentially similar to the multi-layer film structure described above. However, the multi-layer film  200  includes a first colored portion  210  and a second colored portion  220 . The first colored portion  210  includes in sequence an inmost layer  211 , a medium layer  212 , a reflective-transmissive layer  213  and an outmost layer  214 . The second colored portion  220  includes in sequence an inmost layer  221 , a medium layer  222 , a reflective-transmissive layer  223  and an outmost layer  224 . In the present embodiment, substantially the only difference between the layers  211 ,  212 ,  213 ,  214  of the first colored portion  210  and the layers  221 ,  222 ,  223 ,  224  of the second colored portion  220  is that the thickness of the medium layer  212  is different from that of the medium layer  222 . With this configuration, the color appearance of the first colored portion  210  is different from the color appearance of the second colored portion  220 . In alternative embodiments, the inmost layers  211  and  221  can instead be the one same continuous single inmost layer. 
     Referring to  FIG. 3 , a shell  300  of an electric device  301  is provided as an exemplary embodiment of an application environment of a multi-layer film structure. The shell  300  includes an enclosure preform  310  configured as a substrate, and a multi-layer film  320  formed on the enclosure preform  310 . In the illustrated embodiment, the multi-layer film  320  is essentially similar to the multi-layer film  100  described above. That is, the multi-layer film  320  includes in sequence an inmost layer  321 , a medium layer  332 , a reflective-transmissive layer  323  and an outmost layer  324 . 
     It is understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the disclosure.