A mobile phone rear cover film and its preparation method

Abstract

The present invention provides a mobile phone back cover film and a preparation method thereof. The preparation method includes the following steps: (1) coating a layer of PU coating, a layer of OCA optical pressure-sensitive adhesive coating, and a transparent PET release film layer on the upper surface of a wound BOPET film in sequence; (2) coating a layer of PU coating on the lower surface of the wound BOPET film, and then performing semi-transparent color coating on the PU coating to obtain a semi-transparent color layer or performing gradient color printing on the PU coating to obtain a gradient color layer; (3) imprinting a layer of UV pattern layer on the semi-transparent color layer or gradient color layer, then performing coating treatment, then coating a layer of black pressure-sensitive adhesive, and then coating a layer of transparent PET film or black PET film for winding to obtain a mobile phone back cover film. The preparation method of the present invention can greatly reduce the production cost.

Description

Technical Field

[0001] The present invention relates to a mobile phone back cover film and a preparation method thereof. Background Art

[0002] Mobile phones have now become an indispensable tool in people's lives. To meet the different aesthetic requirements of different customers for mobile phone decoration, mobile phone manufacturers have produced different back cover decorative films and functions. To produce back cover films with different effects, current manufacturers of mobile phone back cover films all adopt a production and preparation method of cutting thin films into individual mobile phone back cover films. This method has low production efficiency, requires a large number of production personnel, huge investment, and too high costs.

[0003] Currently, the light-shielding layer in mobile phone back cover films is achieved by the method of multiple screen printings with black ink. It is a single-layer structure. The basic principle of screen printing is: using the principle that the mesh holes in the graphic part of the screen printing plate allow ink to pass through, while the mesh holes in the non-graphic part do not allow ink to pass through for printing. During printing, ink is poured at one end of the screen printing plate, and a certain pressure is applied to the ink part on the screen printing plate with a squeegee, while moving towards the other end of the screen printing plate. The screen equipment includes a screen printing machine and sheet materials.

[0004] Multiple screen printings cause problems such as incomplete printing at the edges, poor printing uniformity, easy uneven thickness of the ink layer at the edges (uniformity ±2um), quality risks caused by color light leakage, high costs, and low qualification rates. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a mobile phone back cover film and a preparation method thereof in view of the defects of the existing production and preparation method of mobile phone back cover films, such as low production efficiency, a large number of production personnel required, huge investment, too high costs, and incomplete printing at the edges, poor printing uniformity, and easy uneven thickness of the ink layer at the edges of the produced mobile phone back cover films. The preparation method of the present invention can greatly reduce production costs. The light-shielding layer of the mobile phone back cover film obtained by the preparation method of the present invention has good printing uniformity at the edges, no color light leakage, good uniformity (±0.2um), and has very good market application prospects.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] The present invention provides a preparation method of a mobile phone back cover film, which includes the following steps:

[0008] (1) A PU coating, an OCA optical pressure-sensitive adhesive coating, and a transparent PET release film layer are sequentially coated on the upper surface of a wound BOPET film;

[0009] (2) After coating a layer of PU coating on the lower surface of the wound BOPET film, a semi-transparent color layer is coated on the PU coating or a gradient color layer is obtained by gradient color printing on the PU coating;

[0010] (3) After imprinting a layer of UV pattern layer on the semi-transparent color layer or gradient color layer, coating treatment is carried out, then a layer of black pressure-sensitive adhesive is coated, and then a transparent PET film or a black PET film is laminated and wound up to obtain a mobile phone back cover film.

[0011] In a preferred embodiment of the present invention, in step (1), the wound BOPET film is preferably coated without cutting.

[0012] In a preferred embodiment of the present invention, the wound BOPET film can be a wound optical grade BOPET film; the thickness is preferably 30-100 um, the haze is preferably less than or equal to 1.0, the light transmittance is preferably greater than or equal to 90%, and the roll length is preferably less than or equal to 100,000 meters.

[0013] In a preferred embodiment of the present invention, in step (1), the thickness of the PU coating can be 1-2 um.

[0014] In a preferred embodiment of the present invention, in step (1), the coating running speed of the PU coating can be 50-80 m / min.

[0015] In a preferred embodiment of the present invention, the thickness of the OCA optical pressure-sensitive adhesive coating can be 20-30 um.

[0016] In a preferred embodiment of the present invention, the coating running speed of the OCA optical pressure-sensitive adhesive coating can be 20-40 m / min.

[0017] In a preferred embodiment of the present invention, in step (1), the thickness of the transparent PET release film layer can be 100 um.

[0018] In a preferred embodiment of the present invention, in step (1), the coating of the OCA optical pressure-sensitive adhesive coating and the transparent PET release film layer is carried out synchronously.

[0019] In a preferred embodiment of the present invention, in step (2), the thickness of the PU coating can be 1-2 um.

[0020] In a preferred embodiment of the present invention, in step (2), the coating running speed of the PU coating can be 50-80 m / min.

[0021] In a preferred embodiment of the present invention, the semi-transparent color material for the semi-transparent color coating is polyurethane ink, preferably the polyurethane ink of DIC Ink Co., Ltd. of Japan, with the model number FZ6600.

[0022] In a preferred embodiment of the present invention, the thickness of the semi-transparent color layer can be 3um - 8um, for example, 5um.

[0023] In a preferred embodiment of the present invention, the running speed of the semi-transparent color layer can be 20 meters per minute - 40 meters per minute, for example, 30 meters per minute.

[0024] In a preferred embodiment of the present invention, the gradient color material for the gradient color printing is polyurethane ink, preferably the polyurethane ink of DIC Ink Co., Ltd. of Japan, with the model number FZ6600.

[0025] In a preferred embodiment of the present invention, the thickness of the gradient color layer can be 1 - 10um.

[0026] In a preferred embodiment of the present invention, the running speed of the gradient color printing can be 30 - 50 meters per minute.

[0027] In a preferred embodiment of the present invention, the UV pattern layer can be obtained by UV glue stamping.

[0028] In a preferred embodiment of the present invention, the thickness of the UV pattern layer can be 5 - 15um.

[0029] In a preferred embodiment of the present invention, the running speed of the stamping can be 10 - 30 meters per minute.

[0030] In a preferred embodiment of the present invention, the material for the coating process is indium tin metal. In the indium tin metal, the mass ratio of indium to tin is preferably 3:7.

[0031] In a preferred embodiment of the present invention, the instrument for the coating process can be a roll-to-roll magnetron sputtering device.

[0032] In a preferred embodiment of the present invention, the running speed of the coating process can be 2 - 20 meters per minute, for example, 5 meters per minute.

[0033] In a preferred embodiment of the present invention, in step (3), the coating is preferably a layer of black pressure-sensitive adhesive coated on the coating film, and a transparent PET film or a black PET film is synchronously laminated.

[0034] In a preferred embodiment of the present invention, the thickness of the black pressure-sensitive adhesive can be 10 - 30um.

[0035] In a preferred embodiment of the present invention, in step (3), the thickness of the transparent PET film can be 10-20 um, for example, 12 um.

[0036] In a preferred embodiment of the present invention, in step (3), the thickness of the black PET film can be 10-20 um, for example, 16 um.

[0037] In a preferred embodiment of the present invention, the preparation method may further include a cutting step; the cutting step may be as follows: cutting the mobile phone back cover film according to a suitable size (such as the size of a mobile phone back cover).

[0038] The present invention provides a mobile phone back cover film obtained by the above preparation method.

[0039] The present invention provides a mobile phone back cover film as described above, whose structure is in turn: a transparent PET release film layer, an OCA optical pressure-sensitive adhesive layer, a PU coating layer, a wound BOPET film layer, a PU coating layer, a semi-transparent color layer or a gradient color layer, a UV pattern layer, a coating, a black optical pressure-sensitive adhesive layer, a transparent PET film layer or a black PET film layer.

[0040] The present invention provides a mobile phone back cover film as described above, whose structure is in turn: a transparent PET release film layer, an OCA optical pressure-sensitive adhesive layer, a PU coating layer, a wound BOPET film layer, a PU coating layer, a semi-transparent color layer, a UV pattern layer, a coating, a black optical pressure-sensitive adhesive layer, a transparent PET release film layer.

[0041] The present invention provides a mobile phone back cover film as described above, whose structure is in turn: a transparent PET release film layer, an OCA optical pressure-sensitive adhesive layer, a PU coating layer, a wound BOPET film layer, a PU coating layer, a gradient color layer, a UV pattern layer, a coating, a black optical pressure-sensitive adhesive layer, a black PET film layer.

[0042] In a preferred embodiment of the present invention, the thickness of the transparent PET release film layer can be 100 um.

[0043] In a preferred embodiment of the present invention, the thickness of the OCA optical pressure-sensitive adhesive coating can be 20-30 um.

[0044] In a preferred embodiment of the present invention, the thickness of the PU coating layer can be 1-2 um.

[0045] In a preferred embodiment of the present invention, the wound BOPET film can be a wound optical grade BOPET film; the thickness is preferably 30-100 um, the haze is preferably less than or equal to 1.0, the light transmittance is greater than or equal to 90%, and the roll length is less than or equal to 100,000 meters.

[0046] In a preferred embodiment of the present invention, the thickness of the semi-transparent color layer can be 3 um - 8 um.

[0047] In a preferred embodiment of the present invention, the thickness of the UV pattern layer can be 5 - 15 um.

[0048] In a preferred embodiment of the present invention, the thickness of the black pressure-sensitive adhesive layer can be 10 - 30 um.

[0049] In a preferred embodiment of the present invention, the thickness of the transparent PET film layer in the "transparent PET film layer or black PET film layer" can be 10 - 20 um.

[0050] In a preferred embodiment of the present invention, the thickness of the black PET film layer in the "transparent PET film layer or black PET film layer" can be 10 - 20 um.

[0051] In a preferred embodiment of the present invention, the structure of the mobile phone back cover film is as follows: transparent PET release film layer, OCA optical pressure-sensitive adhesive layer, PU coating, wound BOPET film layer, PU coating, semi-transparent color layer, UV pattern layer, coating, black optical pressure-sensitive adhesive layer, transparent PET film; wherein, the thickness of the transparent PET release film layer is 100 um; the thickness of the OCA optical pressure-sensitive adhesive coating is 20 um; the thickness of the PU coating is 2 um; the wound BOPET film is a wound optical grade BOPET film with a thickness of 50 um, preferably a haze less than or equal to 1.0, a light transmittance greater than or equal to 90%, and a roll length less than or equal to 100,000 meters; the thickness of the semi-transparent color layer can be 5 um; the thickness of the UV pattern layer is 8 um; the thickness of the black pressure-sensitive adhesive layer is 20 um; the thickness of the transparent PET film layer is 12 um.

[0052] In a preferred embodiment of the present invention, the structure of the mobile phone back cover film is as follows: transparent PET release film layer, OCA optical pressure-sensitive adhesive layer, PU coating, wound BOPET film layer, PU coating, gradient color layer, UV pattern layer, coating, black optical pressure-sensitive adhesive layer, black PET film layer; wherein, the thickness of the transparent PET release film layer is 100 um; the thickness of the OCA optical pressure-sensitive adhesive coating is 15 um; the thickness of the PU coating is 1 um; the wound BOPET film is a wound optical grade BOPET film with a thickness of 50 um, preferably a haze less than or equal to 1.0, a light transmittance greater than or equal to 90%, and a roll length less than or equal to 100,000 meters; the thickness of the gradient color layer can be 2 um; the thickness of the UV pattern layer is 15 um; the thickness of the black pressure-sensitive adhesive layer is 10 um; the thickness of the black PET film layer is 12 um.

[0053] The light-shielding layer of the mobile phone rear cover plate film is a two-layer structure composed of a black optical pressure-sensitive adhesive layer and a layer of PET film layer, which is opaque and realized through a coating process. It can solve the quality risks caused by screen printing used for the light-shielding layer in the current mobile phone rear cover plate film, such as incomplete printing at the edges, poor printing uniformity, uneven thickness of the ink layer at the edges, and color leakage. Among them, the PET film layer can be a transparent PET film layer or a black PET film layer.

[0054] The present invention provides a mobile phone rear cover, which includes the mobile phone rear cover plate film and tempered glass as described above. Preferably, the transparent PET release film of the mobile phone rear cover plate film is removed and bonded to the tempered glass.

[0055] In the present invention,

[0056] BOPET film refers to biaxially oriented polyester film;

[0057] PU coating refers to polyurethane coating;

[0058] OCA optical pressure-sensitive adhesive refers to optical acrylic pressure-sensitive adhesive;

[0059] PET film refers to biaxially oriented polyester film;

[0060] PET release film is a commonly used material in thermal transfer. The substrate is PET film, which is formed by coating silicone oil, and is also called silicone oil film;

[0061] Pressure-sensitive adhesive, commonly known as self-adhesive, is a type of adhesive that is sensitive to pressure.

[0062] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be arbitrarily combined to obtain various preferred embodiments of the present invention.

[0063] The reagents and raw materials used in the present invention are all commercially available.

[0064] The positive and progressive effects of the present invention are as follows:

[0065] The present invention adopts a roll-to-roll production method, which solves the problems of high cost investment in a large number of personnel and equipment and low production efficiency required by the sheet-to-sheet production method in the original application publication number CN104378466A. For each process of the mobile phone rear cover plate film produced by the present invention, such as coating process, UV curing treatment process, magnetron sputtering coating process, black light-shielding coating material process, etc., roll-to-roll continuous production is adopted, thereby obtaining the mobile phone rear cover plate film, significantly improving the production efficiency and greatly reducing the production cost. The present invention can enable the mobile phone rear cover plate film to be produced continuously and on a large scale in a roll-to-roll manner, making the mobile phone rear cover plate film suitable for cutting of various sizes and suitable for bonding to the rear covers of various mobile phone brands.

[0066] The product prepared by the present invention does not have the defects of the products obtained by the prior art using the screen printing method. The overall uniformity of the light-shielding layer is ±0.2um, while the uniformity of the screen printing ink layer is ±2um. Description of the Drawings

[0067] Figure 1 It is a schematic diagram of the structure of the mobile phone back cover film in the embodiment. Among them, 1 is a transparent PET release film layer, 2 is an OCA optical pressure-sensitive adhesive layer, 3 is a PU coating, 4 is a BOPET film layer, 5 is a PU coating, 6 is a semi-transparent color layer or a gradient color layer, 7 is a UV pattern layer, 8 is a coating, 9 is a black optical pressure-sensitive adhesive layer, and 10 is a transparent PET film layer or a black PET film layer. Detailed Embodiments

[0068] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. The experimental methods without specific conditions in the following examples are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0069] The BOPET film and the black PET in the embodiments of the present invention are conventional products in the art; among them, the physical and chemical properties of the BOPET film meet the qualified product indicators of the National Standard of the People's Republic of China GB / T16958-2008 (biaxially oriented polyester film for packaging).

[0070] The manufacturer of PU is Anhui Zhongen Chemical Co., Ltd., model: PU-166.

[0071] The manufacturer of the OCA optical pressure-sensitive adhesive is Guangdong Gulebang New Materials Technology Co., Ltd., model: OP300.

[0072] UV glue, model: PAR-36, Shenzhen Sabis Technology Co., Ltd.

[0073] The manufacturer of the transparent PET release film is Shantou Kaijie Packaging Materials Co., Ltd.

[0074] Polyurethane ink, manufacturer, Japan DIC Ink Co., Ltd.

[0075] Indium tin metal, the mass ratio of indium to tin is 3:7, Shenzhen Zenghua Vacuum Plating Materials Co., Ltd.

[0076] Polyurethane ink: manufacturer: Japan DIC Ink Co., Ltd. model: FZ6600.

[0077] The coating equipment in the embodiments of the present invention is: imported equipment from South Korea (manufacturer: South Korea PRINPIA MACHINERY CO., LTD model: XTB1650-22).

[0078] The winding type UV curing embossing equipment is: imported from South Korea (manufacturer: PRINPIA MACHINERY CO., LTD, South Korea; model: XTB1650-22).

[0079] The winding type magnetron sputtering equipment is: imported from South Korea (Advanced Technologies, Co., Ltd, South Korea), model: MENTO-M.

[0080] The five-color gravure printing equipment is: from Shaanxi Beiren Printing Machinery Co., Ltd, model: FR400ELS.

[0081] The on-line coating thickness measuring device is the device for measuring the thickness change of the micro-coating of aluminized film and the on-line infrared transmission measuring system described in Chinese Patent No. 200820055437.5 and Software Copyright Registration No. 2008SR36733.

[0082] The manufacturer of the black PET film is SKC Group, South Korea, model: SB00.

[0083] The black pressure-sensitive adhesive is purchased from DIC, Japan (DIC Corporation, Japan), model: FZ6600.

[0084] The output and efficiency tests in the embodiments of the present invention are obtained according to the tests of actual production.

[0085] Example 1

[0086] This experiment is calculated according to the production volume of width 1200mm, length 100000 meters, area: 120000 square meters (folding into 1000000 pieces of 300mm * 400mm):

[0087] (1) Select the winding type optical grade BOPET film, the film thickness is 50um, the haze is less than or equal to 1.0, the light transmittance is greater than or equal to 90%, width 1200mm, length 100000 meters.

[0088] (2) Adopt a coating equipment to coat a layer of PU coating on the upper surface of the BOPET, the coating thickness is 2um, and the running speed is 50 meters per minute. A total of 2000 minutes.

[0089] (3) Coat a layer of OCA optical pressure-sensitive adhesive coating on the PU coating, the coating thickness is 20um. The running speed is 20 meters per minute. A total of 5000 minutes.

[0090] (4) While coating the OCA optical pressure-sensitive adhesive layer, isolate and wind it with a layer of transparent PET release film at the same time, and the thickness of the release film layer is 100um.

[0091] (5) Apply a layer of PU coating on the lower surface of BOPET, with a coating thickness of 2 μm and a running speed of 50 m / min. The total time is 2000 minutes.

[0092] (6) Apply a semi-transparent color coating using polyurethane ink on the PU coating to obtain a semi-transparent color layer, with a coating thickness of 5 μm and a running speed of 30 m / min. The total time is 3500 minutes.

[0093] (7) Using a coating device, imprint a layer of UV pattern layer on the lower surface of the semi-transparent color layer with UV glue, with a coating thickness of 8 μm and a running speed of 15 m / min. The total time is 7000 minutes.

[0094] (8) Place the wound film with the UV pattern layer in a wound magnetron sputtering device and perform continuous coating treatment with an indium tin metal product with a mass ratio of 3:7, with a light transmittance of 5% and a running speed of 5 m / min. The total time is 20000 minutes.

[0095] (9) After coating, use a coating device to apply another layer of black pressure-sensitive adhesive, and simultaneously wind it with a layer of transparent PET film. The thickness of the black pressure-sensitive adhesive layer is 20 μm, and the transparent PET film layer is 12 μm. The running speed of coating is the same as that of winding, both are 20 m / min. The total time is 5000 minutes.

[0096] The steps (2)(3)(4)(5)(6)(7)(8)(9) are continuous roll-to-roll production, and the total production time is 44500 minutes (equivalent to 31 days).

[0097] Example 2

[0098] This experiment is calculated according to the production volume of width 1200 mm, length 100000 m, and area: 120000 square meters (equivalent to 1000000 pieces of 300 mm * 400 mm):

[0099] (1) Select a wound optical grade BOPET film with a film thickness of 50 μm, a haze less than or equal to 1.0, a light transmittance greater than or equal to 90%, a width of 1200 mm, and a length of 100000 m.

[0100] (2) Apply a layer of PU coating on the upper surface of BOPET, with a coating thickness of 1 μm and a running speed of 80 m / min. The total time is 1300 minutes

[0101] (3) Apply a layer of OCA optical pressure-sensitive adhesive coating on the PU coating, with a coating thickness of 15 μm. The running speed is 30 m / min. The total time is 3500 minutes

[0102] (4) While coating the OCA optical pressure-sensitive adhesive layer, wind it with a layer of transparent PET release film with a film thickness of 100 μm

[0103] (5) Coat a layer of PU coating on the lower surface of BOPET. The coating thickness is 1 μm, and the running speed is 80 m / min. The total time is 1300 minutes.

[0104] (6) Conduct gradient color printing on the PU coating with polyurethane ink to obtain a gradient color layer. The coating thickness is 2 μm, and the running speed is 50 m / min. The total time is 2000 minutes.

[0105] (7) Stamp a layer of UV pattern on the gradient color layer. The coating thickness is 15 μm, and the running speed is 10 m / min. The total time is 10000 minutes.

[0106] (8) Place the wound film with the UV pattern layer in a wound magnetron sputtering device and conduct continuous coating treatment with an indium tin metal product with a mass ratio of 3:7. The light transmittance is 20%, and the running speed is 10 m / min. The total time is 10000 minutes.

[0107] (9) After coating, coat a layer of black pressure-sensitive adhesive and wind it together with a layer of black PET at the same time. The thickness of the black pressure-sensitive adhesive layer is 10 μm, and the thickness of the black PET layer is 16 μm. The running speed is 20 m / min. The total time is 3500 minutes.

[0108] The operations (2), (3), (4), (5), (6), (7), (8), and (9) are continuous roll-to-roll production, and the total production time is 31600 minutes (equivalent to 22 days).

[0109] Comparative Experiment 1

[0110] The production method of Application Publication No. CN104378466A is sheet-to-sheet production, calculated according to 1000000 sheets with each sheet size of 300 mm * 400 mm.

[0111] Table 1

[0112]

[0113] Table 2 Summary of Comparison of Production Time Efficiency for Producing 1000000 Sheets

[0114] Project Example 1 Example 2 Comparative Example 1 Input personnel person 1 1 275 Input equipment unit 4 4 175 Input time day 31 22 1062

[0115] For the mobile phone back cover film in this example and Comparative Experiment 1, especially the roll-to-roll continuous production process in Example 2, it requires fewer personnel, less equipment, and shorter time. When producing 1000000 mobile phone back covers at a time, the mobile phone back cover film produced by the roll-to-roll production method of the present invention has higher production efficiency and significantly lower costs compared with the prior art of sheet-by-sheet production.

[0116] Effect Example 1

[0117] The uniformity of the light-shielding layer of the mobile phone back cover film obtained by using the coating process of the present invention and the screen printing method was measured with a thickness gauge, and the results are as follows:

[0118]

[0119] Thickness gauge: THI-1801 of Jinan Sike Testing Technology Co., Ltd.

[0120] Mobile phone back cover film obtained by screen printing method: BYD Optical Co., Ltd.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a mobile phone back cover film, characterized in that, it is prepared by a continuous roll-to-roll production process, which includes the following steps: (1) A layer of PU coating, a layer of OCA optical pressure-sensitive adhesive coating, and a transparent PET release film layer are sequentially coated on the upper surface of the wound BOPET film; the wound BOPET film is directly coated without cutting; (2) After coating a layer of PU coating on the lower surface of the wound BOPET film, semi-transparent color coating is performed on the PU coating to obtain a semi-transparent color layer or gradient color printing is performed on the PU coating to obtain a gradient color layer; (3) After imprinting a layer of UV pattern layer on the semi-transparent color layer or gradient color layer, coating treatment is carried out, then a layer of black pressure-sensitive adhesive is coated, and then a transparent PET film or a black PET film is laminated and wound to obtain a mobile phone back cover film.

2. The preparation method according to claim 1, characterized in that, the wound BOPET film is a wound optical grade BOPET film; the thickness is 30-100um, the light transmittance is greater than or equal to 90%, and the roll length is less than or equal to 100,000 meters; and / or, in step (1), the thickness of the PU coating is 1-2um; and / or, in step (1), the coating running speed of the PU coating is 50-80 meters per minute; and / or, the thickness of the OCA optical pressure-sensitive adhesive coating is 20-30um; and / or, the coating running speed of the OCA optical pressure-sensitive adhesive coating is 20-40 meters per minute; and / or, in step (1), the thickness of the transparent PET release film layer is 100um; and / or, in step (1), the coating of the OCA optical pressure-sensitive adhesive coating and the transparent PET release film layer is carried out synchronously.

3. The preparation method according to claim 1, characterized in that, in step (2), the thickness of the PU coating is 1-2um; and / or, in step (2), the coating running speed of the PU coating is 50-80 meters per minute; and / or, the semi-transparent color material for the semi-transparent color coating is polyurethane ink; and / or, the thickness of the semi-transparent color layer is 3um-8um; and / or, the running speed of the semi-transparent color layer is 20 meters per minute - 40 meters per minute; and / or, the gradient color material for the gradient color printing is polyurethane ink; and / or, the thickness of the gradient color layer is 1-10um; and / or, the running speed of the gradient color printing is 30-50 meters per minute.

4. The preparation method according to claim 1, characterized in that, the UV pattern layer is obtained by UV glue imprinting; and / or, the thickness of the UV pattern layer is 5-15um; and / or, the running speed of the imprinting is 10-30 meters per minute; and / or, the material for the coating treatment is indium tin metal; and / or, the instrument for the coating treatment is a wound magnetron sputtering device; and / or, the running speed of the coating treatment is 2-20 meters per minute; And / or, in step (3), the coating is to apply a layer of black pressure-sensitive adhesive on the coating film, and simultaneously laminate a layer of transparent PET film or black PET film; And / or, the thickness of the black pressure-sensitive adhesive is 10-30um; And / or, in step (3), the thickness of the transparent PET release film layer is 10-20um; And / or, in step (3), the thickness of the black PET film is 10-20um.

5. The preparation method according to claim 4, characterized in that in the indium-tin metal, the mass ratio of indium to tin is 3:

7.

6. A mobile phone back cover, characterized in that it includes tempered glass and a mobile phone back cover film prepared by the preparation method of the mobile phone back cover film according to any one of claims 1-5. After removing the transparent PET release film of the mobile phone back cover film, it is bonded to the tempered glass.

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