Decorative film, electronic device back cover, and electronic device

Abstract

The utility model provides a kind of decorative film, including the substrate layer, texture layer, reflection layer and colouring layer set gradually, and the utility model provides a kind of decorative film, electronic equipment back cover and electronic equipment, applied to optical decorative film technical field;The decorative film includes substrate layer, texture layer, reflection layer and colouring layer, texture layer has multiple texture units, texture unit has at least one functional side, functional side includes at least two continuous folds, two folds have different angles of inclination relative to substrate layer Angle of inclination from the angle of inclination of the fold adjacent to substrate layer starts to decrease setting, the utility model solves the light utilization efficiency low, overall brightness insufficient, weak visual level, lack of stereoscopic depth effect and the problems such as monotonous light and shadow effect, unable to realize diversified and dynamic visual expression caused by the insufficient refractive index of texture layer material and serious total reflection in the prior art, and texture design means limited, microstructure design single, light path changes simple.

Description

Technical Field

[0001] This utility model relates to the field of optical decorative film technology, and in particular to a decorative film, an electronic device back cover, and an electronic device. Background Technology

[0002] With the rapid iteration of consumer electronics products, users' aesthetic demands for product appearance are increasing. As a visually appealing component, the decorative effect of a smartphone back cover directly impacts its market competitiveness. Currently, decorative films for smartphone back covers on the market mainly suffer from the following problems:

[0003] Traditional decorative films, even those with micro-textures, generally lack sufficient overall brightness and transparency, appearing dull in low light. Furthermore, their light and shadow effects are mostly simple two-dimensional lines or patterns, lacking rich visual layers and failing to create a striking sense of three-dimensionality and depth. Existing texture designs are mostly periodic, simple geometric structures, such as V-grooves and single-sloping gratings, resulting in monotonous and predictable light and shadow variations, making it difficult to achieve complex, dynamic, and personalized visual effects, thus contributing to the homogenization of product appearances.

[0004] In existing technologies, the refractive index of textured layer materials is typically low, limiting the efficiency of light propagation within the film. Simultaneously, the geometric design of the microstructure is relatively coarse, failing to fully exploit the potential for manipulating the light field through fine geometric construction. While some existing solutions have attempted to alter the macroscopic arrangement, such as using gradient widths, or employing asymmetrical cross-sections, such as a curved surface combined with a plane, none of these address the microscopic geometric reconstruction within individual optical units, resulting in limited performance improvements. Some solutions have even removed the reflective layer to reduce costs, leading to a further decline in optical performance.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this utility model, and therefore may include information that does not constitute prior art known to those skilled in the art. Utility Model Content

[0006] In view of this, the present invention provides a decorative film, an electronic device back cover, and an electronic device to solve the problems of low light utilization efficiency and insufficient overall brightness caused by insufficient refractive index and severe total internal reflection of the texture layer material in the prior art; to solve the problems of weak visual layering and lack of three-dimensional depth effect caused by simple microstructure design and simple light path changes; and to solve the problems of monotonous light and shadow effects and inability to achieve diversified and dynamic visual expression due to limited texture design methods.

[0007] This utility model embodiment provides a decorative film, which includes a substrate layer, a texture layer, a reflective layer and a coloring layer arranged sequentially: the texture layer has multiple texture units;

[0008] The texture unit has at least one functional side, which includes at least two consecutive folds, the angle between the two folds and the substrate layer decreasing from the angle between the folds of the adjacent substrate layer.

[0009] In some optional embodiments, the folded surface is a flat surface.

[0010] In some alternative embodiments, the functional side includes 2 to 8 successively decreasing folds.

[0011] In some alternative embodiments, the texture layer is made of a material with a refractive index of not less than 1.7.

[0012] In some alternative embodiments, the geometry of the texture unit is a prism or a pyramid.

[0013] In some alternative embodiments, the pyramid is a pyramid with N sides, where N is an integer not less than 3, and at least one side is a functional side.

[0014] In some alternative embodiments, the pyramid includes multiple functional sides, the fold angles of which are configured as symmetrical or asymmetrical structures.

[0015] In some optional embodiments, the included angle of at least two folds on the functional side is set in an arithmetic or random decreasing manner along the direction from the fold away from the center of the texture unit to the fold near the center.

[0016] In some alternative embodiments, the included angle ranges from 6° to 24°.

[0017] In some optional embodiments, the height of the texture unit ranges from 2 μm to 30 μm.

[0018] In some alternative embodiments, gaps are provided between multiple texture units, or multiple texture units are arranged closely together without gaps.

[0019] In some optional embodiments, the arrangement period of texture units on the substrate layer is less than 80 μm, so that the texture units are not visible to the naked eye, or the arrangement period of texture units on the substrate layer is not less than 80 μm, so that the texture units are visible to the naked eye.

[0020] In some optional embodiments, the difference between the refractive index of the texture layer and the refractive index of the substrate layer is not less than 0.5.

[0021] In some alternative embodiments, the texture unit further includes auxiliary sides, which are flat surfaces, convex surfaces, concave surfaces, or a combination thereof.

[0022] This utility model provides a back cover for an electronic device, which includes a housing and a decorative film disposed on the housing, the decorative film being as described above.

[0023] This utility model embodiment provides an electronic device, which includes the electronic device back cover as described above.

[0024] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the present invention.

[0025] The decorative film, electronic device back cover, and electronic device of this utility model have the following beneficial effects:

[0026] This decorative film, due to the use of a material with a refractive index of not less than 1.7 in the texture layer, reduces total internal reflection of light within the material, thus improving light utilization. The sides of each texture unit consist of at least two continuous folds with different angles, allowing light to undergo multiple refractions and form multi-layered light paths. Combined with a reflective layer, light can be reflected back to the texture layer, further enhancing the light and shadow effects. This structure enables the decorative film to present a bright and three-dimensional visual effect, and by adjusting the number and angle of the folds and the arrangement of the texture units, diverse light and shadow expressions can be achieved. Attached Figure Description

[0027] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0028] Figure 1 This is a cross-sectional schematic diagram of the overall structure of the decorative film according to one embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the cross-sectional outline of a general texture unit in one embodiment of this utility model;

[0030] Figure 3 This is a schematic diagram of the contour cross-sectional structure of a single texture unit composed of multiple discrete folded surfaces in one embodiment of this utility model.

[0031] Figure 4 This is a schematic diagram of the cross-sectional structure of an asymmetric texture unit in one embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of a symmetrical curved surface profile cross-section structure with decreasing angles for a single texture unit in one embodiment of this utility model. Detailed Implementation

[0033] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted. The words “or” and “or” in the specification may mean “and” or “or”. Although the terms “upper,” “lower,” “between,” etc., may be used in this specification to describe different exemplary features and elements of this application, these terms are used herein only for convenience, such as according to the orientation of the examples in the drawings. Nothing in this specification should be construed as requiring a specific three-dimensional orientation of the structure to fall within the scope of this application. Although “first” or “second,” etc., are used in this specification to denote certain features, they are only for indication of function and not as a limitation on the number or importance of specific features.

[0034] The propagation of light at the interface of different media follows the laws of refraction and reflection. When light enters another medium from one medium, its propagation direction is deflected, the degree of which depends on the difference in refractive index between the two media and the angle of incidence. When light enters a low-refractive-index medium from a high-refractive-index medium at an angle of incidence greater than the critical angle, total internal reflection occurs, preventing light transmission. The manipulation of light through microstructures is based on the principles of diffraction and interference. When light passes through a microstructure with a size similar to its wavelength, diffraction occurs, and different diffracted beams interfere with each other, forming a specific intensity distribution. By controlling the geometric parameters of the microstructure, precise control over the direction of light propagation and the intensity distribution can be achieved. In this technical solution, the application of high-refractive-index materials aims to improve the efficiency of light entering the texture layer and reduce total internal reflection losses; the design of the multi-faceted structure aims to achieve complex manipulation of light through multiple refractions and diffractions, constructing rich optical paths to achieve specific lighting effects.

[0035] like Figure 1 As shown, this embodiment provides a decorative film, which includes: a substrate layer 100, a texture layer 200, a reflective layer 300, and a coloring layer 400.

[0036] The substrate layer 100 is an optically transparent film used to provide support for the textured layer 200. In this embodiment, the substrate layer 100 is a polyethylene terephthalate (PET) film with a thickness of 75 micrometers. In other embodiments, the substrate layer 100 may also be a polycarbonate (PC) film or a polyimide (PI) film with a thickness ranging from 50 micrometers to 125 micrometers.

[0037] A texture layer 200 is disposed on top of the substrate layer 100 and has multiple texture units. Each texture unit has at least one functional side. (Refer to...) Figure 2 The functional side includes at least two consecutive folds, and the angle between these two folds and the substrate layer 100 decreases (e.g., to 12° and 6°) starting from the angle of the fold adjacent to the substrate layer (e.g., the fold with an angle of 18°). In this embodiment, the folds are all flat surfaces.

[0038] In this embodiment, the texture layer 200 is made of a material with a refractive index, preferably not less than 1.7. Specifically, the texture layer 200 is made of an ultraviolet (UV) curable resin doped with titanium nanoparticles, and the UV curable resin has a measured refractive index of 1.75 after being cured by a UV nanoimprinting process.

[0039] In other alternative embodiments, the texture layer 200 may also be made of chalcogenide glass with a refractive index of 2.0 or higher, which can be formed by hot stamping; or the texture layer 200 may also be made of polycarbonate (PC) composite material doped with zirconium dioxide nanoparticles.

[0040] The texture layer 200 is constructed using a material with a refractive index of not less than 1.7, which increases the critical angle for total internal reflection when light travels from the texture layer 200 to the air. This significantly reduces the useless reflection loss of light within the texture layer 200 and improves the light utilization efficiency. Combined with the "multi-faceted blazing structure" of this invention, it solves the technical problem of low overall brightness caused by insufficient material refractive index in the prior art.

[0041] A reflective layer 300 is conformally disposed on the surface of the textured layer 200 to reflect light passing through the textured layer 200. In this embodiment, the reflective layer 300 is a silver (Ag) thin film with a thickness of 80 nanometers (nm) deposited by magnetron sputtering. In other embodiments, the reflective layer is an indium thin film of 80-300 nm, or a high-reflectivity film with a reflectivity of 60-90%.

[0042] A coloring layer 400 is disposed on top of the reflective layer 300 to provide a dark background and enhance light and shadow contrast. In this embodiment, the coloring layer 400 is a 15-micron-thick black ink layer formed by screen printing.

[0043] This embodiment constructs a microscopic "multi-faceted shimmering structure" by setting multiple continuous flat folds with different angles on the functional side of the texture unit 310. When light is incident, under the synergistic effect of this structure and the reflective layer 300, the light will undergo complex and multi-layered refraction and reflection paths, thereby solving the technical problems of weak depth effect and monotonous light and shadow effect caused by the single light path in the prior art. Ultimately, the decorative film presents a visual effect of high brightness, strong three-dimensionality and dynamic light and shadow.

[0044] In some embodiments, a decorative film is provided, the structure of which is basically the same as that of the above embodiments, except that the texture unit 310 of the texture layer 200 has a prism geometry, which constitutes a prism unit and is arranged in an array.

[0045] Specifically, each functional side of a prism unit consists of three consecutive flat folds. (See reference...) Figure 3 The structure shown has three folds with angles relative to the substrate layer 100 that can be set to 18°, 12° and 6° respectively.

[0046] In this embodiment, the "multi-faceted shimmering structure" composed of multiple continuous facets at different angles constructs a precise "optical path staircase" for light at the microscopic scale. When a beam of parallel light shines on this structure, part of the light exits from the first facet (18° facet), which is shallower and has a larger angle; the other part of the light propagates to a deeper position in the structure and then exits sequentially from the second facet (12° facet) with a smaller angle and the third facet (6° facet) with the smallest angle. Because these three parts of light experience different propagation path lengths within the texture unit 310, a significant optical path difference is formed between them. Therefore, when the observer's viewing angle moves slightly, the human eye receives a dynamic combination of light signals from different geometric depths and different exit angles. This richly layered optical information encoded by the fine microstructure is ultimately perceived by the human brain as a profound sense of three-dimensional depth, as if the pattern is suspended above the substrate.

[0047] In some embodiments, a decorative film is provided, the structure of which is basically the same as that in the above embodiments, except that the texture unit 310 of the texture layer 200 has a pyramidal geometry.

[0048] In one specific implementation, the pyramid is a pyramid with N functional sides, where N is an integer not less than 3, and at least one side is a functional side. For example, the pyramid can be a quadrangular pyramid. Each quadrangular pyramid unit has a square base and four sides, each side consisting of three consecutive flat folds. In this symmetrical implementation, the fold angles of the four sides are all the same; for example, the angles between these three folds and the base plane, from the base to the apex, can be set to 18°, 12°, and 6° respectively. Because the pyramid structure has sides in multiple directions, its light effect is divergent, ultimately creating a dazzling, diamond-like effect.

[0049] Furthermore, the pyramid has N lateral faces, at least one of which is a functional lateral face of the aforementioned embodiment. In a preferred implementation, all lateral faces of the pyramid are functional lateral faces, and each functional lateral face is composed of multiple successively decreasing facets.

[0050] In a preferred embodiment, the fold angles of the multiple sides of the pyramid can be configured as symmetrical or asymmetrical structures. When the fold angles of the multiple sides are all symmetrical, the sequence of fold angles of all functional sides is the same; for example, all sides are combinations of 18°, 12°, and 6°.

[0051] When multiple sides have asymmetrical folding angles, at least two functional sides will have different folding angle sequences. Please refer to [link / reference]. Figure 4 The illustration depicts an asymmetrical texture unit 310. Specifically, taking a quadrangular pyramid as an example, assuming a direction perpendicular to the substrate layer as a reference, the included angles of the four facets on the opposite first and third sides are set to 6°, 18°, 12°, and 24°, respectively; while the included angles of the four facets on the other two opposite second and fourth sides are set to 8°, 19°, 20°, and 24°, respectively. Through this asymmetrical angle setting, the optical response characteristics of the first and third sides differ from those of the second and fourth sides. When the decorative film or the tilted decorative film is observed from different azimuth angles, due to the different reflection and refraction paths of light on the sides with different characteristics, obvious changes in light and shadow flow and dynamic asymmetry effects will be observed, thus producing a unique and more dynamic visual experience.

[0052] In other embodiments, the pyramid can also be a polyhedral pyramid structure such as a triangular pyramid, pentagonal pyramid, or hexagonal pyramid. The number of facets constituting each side can also be adjusted to two, four, or more as needed for the design.

[0053] In some embodiments, a decorative film is provided, the structure of which is basically the same as that in the above embodiments, except that the included angles of at least two folds on one side of the texture unit 310 decrease arithmetically or randomly along the direction from the fold away from the center of the texture unit 310 to the fold near the center. In one specific implementation, the included angles of multiple folds on a functional side are set in arithmetically decreasing order. For example, with 18° as the first term and a tolerance of -6°, a sequence is formed: 18°, 12°, 6°. In another specific implementation, the included angles can also be set in a random decreasing order, that is, the included angle of the later fold is smaller than the previous one, but the difference is not fixed. For example, a sequence is formed: 22°, 15°, 8°.

[0054] Specifically, taking a pyramidal side with three consecutive flat folds as an example, the angles between the three folds and the substrate layer 100, from the base to the apex of the pyramid, can be set to 22°, 15°, and 8° respectively. With this decreasing setting, the refraction path of light within the texture unit 310 is systematically and progressively deflected, helping to efficiently focus light energy towards a specific viewing direction, thereby enhancing the shimmering effect and three-dimensionality of the decorative film.

[0055] In other implementations, the number of folds can be two or four, and their included angles also follow a decreasing pattern. For example, for a structure with two folds, the included angles can be set to 20° and 10°; for a structure with four folds, the included angles can be set to 23°, 17°, 11°, and 5°.

[0056] In some embodiments, a decorative film is provided, the structure of which is basically the same as that of the above embodiments, except that the included angle of the folded surface of the texture unit 310 ranges from 6° to 24°.

[0057] In one specific implementation, taking a prism side with two consecutive flat folds as an example, the included angle of the first fold is set to 18°, and the included angle of the second fold is set to 8°.

[0058] In another specific implementation, to achieve a particular optical effect, the included angle of the first fold can be set to 6°, and the included angle of the second fold can be set to 24°. All included angle values ​​in both implementations fall within the range of 6° to 24°. By controlling the included angles of the folds within this range, a good balance can be achieved between achieving significant light and shadow effects and ensuring technological feasibility.

[0059] In some embodiments, a decorative film is provided, the structure of which is basically the same as that in the above embodiments, except that the height of the texture unit 310 ranges from 2μm to 30μm.

[0060] In a specific implementation, refer to Figure 3 The height H of the texture unit 310 shown in the diagram is set to 15 μm in one specific implementation. In other implementations, the height of the texture unit 310 can also be set to 5 μm, 10 μm, 20 μm or 25 μm, depending on the required optical effects and process conditions.

[0061] By controlling the height of the texture unit 310 within the range of 2μm to 30μm, it is possible to ensure that light is effectively refracted on the folded surface to form sufficient optical path difference and three-dimensional depth of field. At the same time, it avoids increasing the manufacturing difficulty and defect rate of the UV nanoimprinting process due to excessive structure height, thus ensuring the high quality and mass production stability of the product.

[0062] In some embodiments, a decorative film is provided, the structure of which is basically the same as that of the above embodiments, except that a gap is provided between adjacent texture units 310 in the array of texture units 310.

[0063] Specifically, taking a prism array as an example, a flat gap with a width of 20μm is set between two adjacent prism units. Because this gap area lacks a "multi-faceted blazing structure", it cannot effectively converge and reflect light and appears as a dark area, thus making the entire decorative film macroscopically present a grating stripe effect of alternating light and dark.

[0064] In other implementations, the width of the gap can be set to the range of 10 μm to 30 μm. The shape of the gap is not limited to a flat surface; it can be a microstructured surface with minute protrusions, depressions, or a specific curvature. Furthermore, the arrangement of the gaps can be regular or irregular, for example, setting gaps of different widths in different areas to form a specific pattern.

[0065] In some embodiments, a decorative film is provided, the structure of which is basically the same as that of the above embodiments, except that in the array of texture units 310, adjacent texture units 310 are arranged closely without gaps.

[0066] Specifically, a precisely designed UV nanoimprint mold is used, in which there are no gaps between the cavities used to form the texture units 310. Under controlled process conditions of appropriate imprinting pressure, temperature, and UV curing energy, the UV-curable resin is ensured to completely fill the mold cavities, thereby forming a gapless prism array on the substrate layer 100. Observation of the surface of the prepared texture layer 200 using atomic force microscopy (AFM) or scanning electron microscopy (SEM) shows that, within the resolution range of the instruments, there are no obvious gaps or flat areas between adjacent prism units.

[0067] The seamless, tightly packed structure ensures that the entire visible surface of the decorative film is covered by the "multi-faceted shimmering structure," avoiding dark areas caused by gaps and ultimately presenting a uniform, uninterrupted, high-brightness visual effect across the entire surface.

[0068] In some embodiments, a decorative film is provided, the structure of which is basically the same as that in the above embodiments, except that the arrangement period of the texture units 310 on the substrate layer is less than 80μm, so that the texture units 310 are not visible to the naked eye.

[0069] In one specific implementation, the arrangement period of the texture units 310 (the distance between the centers of adjacent texture units 310) is set to 50 μm. At this period, because it is less than the visual resolution limit of the human eye, an observer cannot macroscopically distinguish the pattern of individual texture units 310. The entire decorative film presents a uniform, continuous, dynamic gloss with a special sense of depth, rather than specific lines or patterns.

[0070] In other implementations, the arrangement period can also be set to 40μm, 60μm, or 75μm. The arrangement can be periodic or pseudo-random to eliminate potential moiré fringe effects.

[0071] In some embodiments, a decorative film is provided, the structure of which is basically the same as that in the above embodiments, except that the arrangement period of the texture units 310 on the substrate layer is not less than 80μm, so that the texture units 310 are visible to the naked eye.

[0072] In a specific implementation, refer to Figure 3 The texture unit 310 illustrated in the diagram has a period L, with the arrangement period L set to 50 μm. At this period, because it exceeds the visual resolution limit of the human eye, an observer can clearly distinguish the individual bright lines formed by each prism unit on a macroscopic scale. Depending on design requirements, by adjusting the size of this visible period (e.g., 120 μm), the density of the visible bright lines can be changed, thereby forming figurative light and shadow patterns of different styles.

[0073] In some embodiments, a decorative film is provided, the structure of which is basically the same as that in the above embodiments, except that the reflective layer 300 is a multilayer film structure composed of 2 to 8 film layers.

[0074] In one specific implementation, the reflective layer 300 is a five-layer dielectric film mirror (DBR) deposited on the surface of the textured layer 200 using a vacuum deposition process. This multilayer film structure consists of alternating stacks of titanium dioxide (TiO2) and silicon dioxide (SiO2) films. Specifically, the film structure, starting from the side closest to the textured layer 200, is as follows:

[0075] First layer: 50nm thick titanium dioxide film;

[0076] The second layer: an 80nm thick silicon dioxide film;

[0077] The third layer: a 50nm thick titanium dioxide film;

[0078] Fourth layer: 80nm thick silicon dioxide film;

[0079] Fifth layer: 50nm thick titanium dioxide film.

[0080] By employing this multilayer dielectric film structure as the reflective layer 300, a higher reflectivity than traditional single-metal reflective films (such as silver and aluminum) can be achieved, thereby significantly improving the overall brightness of the decorative film. Furthermore, by precisely controlling the thickness of each dielectric material layer, selective modulation of the reflection spectrum can be achieved, thus endowing the decorative film with specific structural colors, such as exhibiting a blue or bluish-purple luster, greatly enriching the color variations of the light and shadow effects.

[0081] In other implementations, the multilayer film can also be made of a combination of zirconium oxide and aluminum oxide. The number of layers and the thickness of each layer can be adjusted according to the desired color and reflective effect.

[0082] In some embodiments, a decorative film is provided, the structure of which is basically the same as that of the above embodiments, except that the difference between the refractive index of the texture layer 200 and the refractive index of the substrate layer 100 is not less than 0.5.

[0083] In one specific implementation, the substrate layer 100 is an optical-grade PET film with a refractive index of 1.50. The texture layer 200 uses a UV-curable resin doped with titanium dioxide nanoparticles. By adjusting the doping concentration of the nanoparticles, the refractive index after curing is set to 2.0. Therefore, the refractive index difference Δn between the texture layer 200 and the substrate layer 100 is calculated as: Δn = 2.0 - 1.50 = 0.5.

[0084] By ensuring a refractive index difference of not less than 0.5 between the texture layer and the substrate layer, Fresnel reflection loss at the interface between the two can be effectively reduced, allowing more incident light to enter the interior of the texture layer 200 and be modulated by its microstructure, thereby improving the light utilization efficiency and final visual brightness of the entire decorative film.

[0085] In an alternative implementation, the structure constituting the side surface of the texture unit 310 can also be a continuously varying curved surface. For example... Figure 5 As shown, on the contour line of this surface, the angles between the tangents at each point from the bottom edge to the top vertex and the substrate plane decrease progressively. For example, the tangent angle at the bottom edge is 18°, while at some point in the middle, the tangent angle decreases to 12°. This surface structure with decreasing tangent angles can also create a "light path staircase," achieving a depth-of-field effect similar to that of discrete folded surfaces.

[0086] In a preferred embodiment, the texture unit further includes auxiliary sides. For example, a prism-shaped texture unit may have one side as the aforementioned functional side (composed of multiple successively decreasing flat folds), while its other side, the auxiliary side, may be a complete flat surface, or a convex or concave curved surface. By combining the functional side with auxiliary sides of different shapes, a richer and more diverse asymmetrical lighting effects can be created.

[0087] This utility model also provides a back cover for an electronic device, which includes a housing and a decorative film disposed on the inner surface of the housing. The decorative film can be the decorative film of any of the foregoing embodiments.

[0088] In one specific implementation, the housing is a 0.8 mm thick transparent glass cover, such as Corning's tempered glass. The decorative film is attached to the inner surface of the housing, i.e., the side facing the inside of the electronic device, by a 50-micron thick layer of optically clear adhesive (OCA).

[0089] In other embodiments, the housing may also be made of a transparent polymer material such as polycarbonate (PC).

[0090] By combining the decorative film with high brightness, strong depth of field and dynamic light and shadow effects of any of the foregoing embodiments with a transparent shell, the back cover of the electronic device obtained in this embodiment has a unique and highly attractive appearance.

[0091] This utility model also provides an electronic device, such as a smartphone, comprising a main body and a back cover assembled to the back of the main body. The back cover is the same as the one described in the above embodiment.

[0092] In one specific implementation, the main body includes a mid-frame structure made of metal or composite material, which houses electronic components such as batteries and circuit boards. The back cover of the electronic device is detachably or non-detachably fixed to the main body by adhesive or snap-fit, thus forming a complete electronic device casing.

[0093] Because the electronic device in this embodiment uses the aforementioned back cover with innovative optical effects, its overall appearance presents a dazzling, diamond-like shimmering effect, greatly enhancing the product's aesthetic value and market recognition.

[0094] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the protection scope of the present invention.

Claims

1. A decorative film comprising a substrate layer, a textured layer, a reflective layer, and a coloring layer disposed sequentially, characterized in that: The texture layer has multiple texture units; The texture unit has at least one functional side, the functional side including at least two consecutive folds, the angle between the two folds and the substrate layer decreasing from the angle between the folds adjacent to the substrate layer.

2. The decorative film as described in claim 1, characterized in that, The folded surface is a flat surface.

3. The decorative film as described in claim 2, characterized in that, The functional side comprises 2-8 consecutively decreasing folds.

4. The decorative film as described in claim 1, characterized in that, The textured layer is made of a material with a refractive index of not less than 1.

7.

5. The decorative film as described in claim 1 or 2, characterized in that, The geometry of the texture unit is a prism or a pyramid.

6. The decorative film as described in claim 5, characterized in that, The pyramid is a pyramid with N sides, where N is an integer not less than 3, and at least one side is the functional side.

7. The decorative film as described in claim 5, characterized in that, The pyramid includes multiple functional sides, and the fold angles of the multiple functional sides are set to a symmetrical or asymmetrical structure.

8. The decorative film as described in claim 1, characterized in that, The included angles of at least two folds on the functional side are set in an arithmetic or random decreasing manner along the direction from the fold away from the center of the texture unit to the fold near the center.

9. The decorative film as described in claim 1, characterized in that, The included angle ranges from 6° to 24°.

10. The decorative film as described in claim 1, characterized in that, The height of the texture unit ranges from 2μm to 30μm.

11. The decorative film as claimed in claim 1, characterized in that, The multiple texture units are spaced apart, or the multiple texture units are arranged closely together without gaps.

12. The decorative film as claimed in claim 1, characterized in that, The arrangement period of the texture units on the substrate layer is less than 80 μm, so that the texture units are not visible to the naked eye; or, the arrangement period of the texture units on the substrate layer is not less than 80 μm, so that the texture units are visible to the naked eye.

13. The decorative film as described in claim 1, characterized in that, The difference between the refractive index of the textured layer and the refractive index of the substrate layer is not less than 0.

5.

14. The decorative film as described in claim 1, characterized in that, The texture unit also includes auxiliary sides, which are flat surfaces, convex arc surfaces, concave arc surfaces, or a combination thereof.

15. A back cover for an electronic device, characterized in that, It includes a housing and a decorative film disposed on the housing, the decorative film being the decorative film as described in any one of claims 1 to 14.

16. An electronic device, characterized in that, It includes the back cover of the electronic device as described in claim 15.

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