An omr membrane, its preparation method and use

Abstract

This invention provides an OMR film, its preparation method, and its application. The OMR film comprises a substrate layer, an outer texture master layer, an outer texture sub-mold layer, and an inner texture layer stacked sequentially. The outer texture sub-mold layer is prepared using a first polyurethane acrylate UV adhesive. The inner texture layer is prepared using a second polyurethane acrylate UV adhesive. The second polyurethane acrylate UV adhesive comprises multifunctional acrylate additives. The OMR film provided by this invention reduces the number of crosslinking varnish layers, resulting in a simpler structure, lower appearance defect rate, excellent mechanical properties and aging resistance, fewer production steps and lower costs, while also reducing VOC emissions and mitigating environmental pollution.

Description

Technical Field

[0001] This invention belongs to the field of OMR membrane manufacturing technology, specifically relating to an OMR membrane, its preparation method, and its application. Background Technology

[0002] In the current mainstream OMR membrane manufacturing process, the "outer texture layer" and "inner texture layer" of the membrane need to be bonded together using "screen printing crosslinking varnish". However, this process has the following drawbacks:

[0003] (1) High risk of appearance defects in OMR film: The screen printing process needs to be operated in an open or semi-open environment, which can easily introduce lint, dust and tiny impurity particles from the environment, resulting in defects such as "particle spots" and "scratches" on the surface of OMR film. The appearance defect rate of OMR film is usually higher than 15%, which cannot meet the quality requirements of "zero visible defects" for high-end consumer electronics (such as mobile phone back covers and display screen decorative films).

[0004] (2) High process complexity: The screen printing bridge varnish process requires additional screen printing equipment and drying and curing equipment, and the uniformity of screen printing thickness (usually 5-10μm) needs to be controlled, which increases the complexity of the production process and the cost of manual intervention.

[0005] (3) Poor environmental performance: Traditional cross-linking varnishes contain volatile organic compounds (VOCs), which release harmful gases during the curing process, failing to meet the current environmental regulations on VOC emission limits for the electronics manufacturing industry.

[0006] Therefore, there is an urgent need to develop a new type of OMR film that does not require screen printing of crosslinking varnish. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide an OMR film, its preparation method, and its application. By designing the raw materials for the inner and outer textured layers of the OMR film, the OMR film possesses excellent mechanical properties and aging resistance. At the same time, it solves the problems of poor appearance and high VOC emissions caused by the use of "screen printing and bridging varnish process" in the production of existing OMR films, thus meeting the application requirements of high-end consumer electronics products (such as smartphones, tablets, and laptops) with stringent appearance quality requirements.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides an OMR film, the OMR film comprising a substrate layer, an outer texture master layer, an outer texture sub-mold layer and an inner texture layer stacked sequentially; the outer texture sub-mold layer is prepared by a first polyurethane acrylate UV adhesive; the inner texture layer is prepared by a second polyurethane acrylate UV adhesive; the second polyurethane acrylate UV adhesive comprises a multifunctional acrylate additive.

[0010] The OMR film provided by this invention has excellent aging resistance (such as UV aging). The multifunctional acrylate additives will chemically crosslink with the active groups (such as hydroxyl groups, double bonds, etc.) in the outer texture sub-mold layer to form an integrated structure of "outer texture sub-mold layer-inner texture layer". It can have strong adhesion without the need for a crosslinking varnish layer, which can meet the mechanical performance requirements (such as adhesion) of the OMR film. It can also eliminate the "screen printing crosslinking varnish" process, thus making the OMR film have a low appearance defect rate, low production cost, and low VOC emissions.

[0011] In this invention, the multifunctional acrylate additives include difunctional acrylate additives.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0013] As a preferred technical solution, the material of the substrate layer includes any one or a combination of at least two of polyethylene terephthalate, polycarbonate, or polyolefin; the substrate layer has high transparency and bending resistance.

[0014] Preferably, the thickness of the substrate layer is 0.1-0.3 mm, for example, it can be 0.12 mm, 0.14 mm, 0.16 mm, 0.18 mm, 0.2 mm, 0.22 mm, 0.24 mm, 0.26 mm, 0.28 mm, etc.

[0015] Preferably, the thickness of the outer texture master mold layer is 10-15 μm, for example, it can be 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, etc.

[0016] Preferably, the raw materials for preparing the outer texture master mold layer include a third type of polyurethane acrylate UV adhesive.

[0017] Preferably, the tensile strength of the third polyurethane acrylate UV adhesive after curing is 10-20 MPa, for example, it can be 10.5 MPa, 11 MPa, 11.5 MPa, 12 MPa, 12.5 MPa, 13 MPa, 14 MPa, 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, etc.

[0018] In this invention, the tensile strength of the third polyurethane acrylate UV adhesive after curing was tested according to GB / T 7124-2008, wherein the curing condition was 2500 mJ / cm. 2 The curing time is 20 seconds.

[0019] The outer texture master mold layer is prepared using high-strength polyurethane acrylate UV adhesive, which is easier to separate from the outer texture sub-mold layer during use; the third polyurethane acrylate UV adhesive can be purchased, for example, it can be purchased from, but not limited to, Huizhou Deyouwei New Material Co., Ltd.'s 3361-WG0558.

[0020] Preferably, the thickness of the outer textured sub-mold layer is 15-20 μm, for example, it can be 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, etc.

[0021] Preferably, the components of the first polyurethane acrylate UV adhesive include a first polyurethane acrylate photosensitive resin, a first initiator, a first monomer, and additives.

[0022] Preferably, the first polyurethane acrylate photosensitive resin comprises toluene diisocyanate, polyether diol, β-hydroxypropyl methacrylate, and Sn. 4+ Photosensitive resin synthesized using catalyst and hydroquinone polymerization inhibitor.

[0023] Preferably, based on the mass of the first polyurethane acrylate photosensitive resin as 100%, the mass of the first initiator is 5-8% (e.g., 5.2%, 5.4%, 5.6%, 5.8%, 6%, 6.2%, 6.4%, 6.6%, 6.8%, 7%, 7.2%, 7.4%, 7.6%, 7.8%, etc.), the mass of the first monomer is 25-30% (e.g., 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, etc.), and the mass of the additives is 5-10% (e.g., 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, etc.).

[0024] Preferably, the first polyurethane acrylate UV adhesive is 3361-WG0655 from Huizhou Deyouwei New Materials Co., Ltd.

[0025] Preferably, the ultraviolet blocking rate of the outer textured sub-mold layer is ≥90%, and the outer textured sub-mold layer can protect the inner textured layer from the effects of ultraviolet aging.

[0026] In this invention, the UV blocking rate of the outer textured sub-mode layer is obtained according to GB / T 2680-2021.

[0027] The pencil hardness after secondary curing of the outer textured sub-mold layer can reach over 2H / kg.

[0028] Preferably, the components of the second polyurethane acrylate UV adhesive further include a second polyurethane acrylate photosensitive resin, a second initiator, and a second monomer.

[0029] Preferably, the multifunctional acrylate additive includes 1,6-hexanediol diacrylate.

[0030] Preferably, the second polyurethane acrylate photosensitive resin comprises toluene diisocyanate, polyether diol, β-hydroxypropyl methacrylate, and Sn. 4+ Photosensitive resin synthesized using catalyst and hydroquinone polymerization inhibitor.

[0031] Preferably, the number average molecular weight of the second polyurethane acrylate photosensitive resin is 500-5000 g / mol, for example, it can be 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 3500 g / mol, 4000 g / mol, 4500 g / mol, etc.

[0032] Preferably, based on the mass of the second polyurethane acrylate photosensitive resin as 100%, the mass of the second initiator is 1-5% (e.g., 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, etc.), and the mass of the second monomer is 10-20% (e.g., 11%, 12%, 13%, 14%, 15%, 15.2%, 15.5%, 15.8%, 16%, 16.2%, 16.5%). The polyfunctional acrylate additives are 5-10% by mass (e.g., 16.8%, 17%, 17.2%, 17.5%, 17.8%, 18%, 18.2%, 18.5%, 18.8%, 19%, 19.2%, 19.5%, 19.8%, etc.).

[0033] Preferably, the second polyurethane acrylate UV adhesive is 3361-WG0579 from Huizhou Deyouwei New Materials Co., Ltd.

[0034] Preferably, the thickness of the inner texture layer is 8-15 μm, for example, it can be 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, etc.

[0035] Preferably, the OMR membrane further includes a functional layer; the functional layer is disposed on the surface of the inner texture layer away from the outer texture sub-mold layer.

[0036] Preferably, the functional layer includes a coating layer and an ink layer stacked together; the coating layer is located near the surface of the inner texture layer and away from the outer texture sub-mold layer.

[0037] Preferably, the thickness of the coating layer is 0.1-0.4 μm, for example, it can be 0.12 μm, 0.15 μm, 0.18 μm, 0.2 μm, 0.22 μm, 0.25 μm, 0.28 μm, 0.3 μm, 0.32 μm, 0.35 μm, 0.38 μm, etc.; the coating layer can form a metallic texture and color effect surface.

[0038] Preferably, the material of the coating layer includes any one or a combination of at least two of SiO2, TiO2, or ZrO2.

[0039] Preferably, the thickness of the ink layer is 10-25 μm, for example, it can be 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, etc.

[0040] Preferably, the material of the ink layer includes black polyurethane ink.

[0041] In a second aspect, the present invention provides a method for preparing an OMR membrane as described in the first aspect, the method comprising:

[0042] The OMR film is obtained by sequentially stacking a substrate layer, an outer texture master layer, an outer texture sub-mold layer, and an inner texture layer.

[0043] Preferably, the preparation method specifically includes the following steps:

[0044] (1) The raw material for preparing the outer texture master mold layer is transferred onto one surface of the substrate layer and then cured to form the outer texture master mold layer;

[0045] (2) The raw material for preparing the outer texture sub-mold layer is transferred onto the surface of the outer texture master mold layer away from the substrate layer, and then cured to form the outer texture sub-mold layer;

[0046] (3) The raw material for preparing the inner texture layer is transferred onto the surface of the outer texture sub-mold layer away from the outer texture master mold layer, and then cured to form the inner texture layer, thus obtaining the OMR film.

[0047] Preferably, the transfer in step (1) is performed using a UV transfer process.

[0048] Preferably, the curing in step (1) is completed by ultraviolet light irradiation, with a light energy of 2000-3000 mJ / cm². 2 For example, it can be 2100 mJ / cm 2 2200 mJ / cm 2 2300 mJ / cm 2 2400 mJ / cm 2 2500 mJ / cm 2 2600 mJ / cm 2 2700 mJ / cm 2 2800 mJ / cm 2 2900 mJ / cm 2 Exposure time is 8-12 seconds, for example, 8.5 seconds, 9 seconds, 9.5 seconds, 10 seconds, 10.5 seconds, 11 seconds, 11.5 seconds, etc.

[0049] Preferably, the transfer in step (2) is performed using a UV transfer process.

[0050] Preferably, the curing in step (2) is completed by ultraviolet light irradiation, with a light energy of 300-500 mJ / cm². 2 For example, it can be 320 mJ / cm 2 340 mJ / cm 2 360 mJ / cm 2 380 mJ / cm 2 400 mJ / cm 2 420 mJ / cm 2 440 mJ / cm 2 460 mJ / cm 2 480 mJ / cm 2 Exposure time is 20-30 seconds, for example, 21 seconds, 22 seconds, 23 seconds, 24 seconds, 25 seconds, 26 seconds, 27 seconds, 28 seconds, 29 seconds, etc.

[0051] Preferably, the transfer process in step (3) is performed using a UV transfer process.

[0052] Preferably, the curing in step (3) is completed by ultraviolet light irradiation, with a light energy of 800-1300 mJ / cm². 2 For example, it can be 850 mJ / cm 2 900 mJ / cm 2 950 mJ / cm 2 1000 mJ / cm 2 1050 mJ / cm 2 1100 mJ / cm 2 1150mJ / cm 2 1200 mJ / cm 2 1250 mJ / cm 2 Exposure time is 10-20 seconds, for example, 11 seconds, 12 seconds, 13 seconds, 14 seconds, 15 seconds, 16 seconds, 17 seconds, 18 seconds, 19 seconds, etc.

[0053] Preferably, after the curing is completed in step (3), the method further includes setting a functional layer on the surface of the inner texture layer away from the outer texture sub-mold layer.

[0054] Preferably, the functional layer is configured using the following method, the method comprising:

[0055] A coating layer is formed by PVD vapor deposition of a material on the surface of the inner texture layer away from the outer texture sub-mold layer.

[0056] The material of the ink layer is screen-printed on the surface of the coating layer away from the inner texture layer, and then a first curing is performed to form the ink layer, thus completing the setting of the functional layer.

[0057] Preferably, the first curing temperature is 80-100℃, for example, it can be 82℃, 84℃, 86℃, 88℃, 90℃, 92℃, 94℃, 96℃, 98℃, etc., and the time is 30-90min, for example, it can be 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, etc.

[0058] Thirdly, the present invention provides an application of the OMR membrane as described in the first aspect in a mobile phone, tablet computer or laptop computer.

[0059] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) The appearance quality of the OMR membrane provided by the present invention is greatly improved. After eliminating the screen printing and bridging varnish process, the amount of environmental impurities introduced is reduced by more than 80%. In actual production, the appearance particle defect rate of the OMR membrane can be controlled at 3.5-5.1%.

[0062] (2) The OMR membrane provided by this invention has a simple process, reduces the investment in screen printing equipment and crosslinking varnish drying equipment, and reduces equipment costs by about 30%. It also eliminates the need for crosslinking varnish material (unit price about RMB 200 / kg) and screen printing labor, reducing the production cost of OMR membrane per square meter by RMB 20-30. Furthermore, it can reduce VOC emissions to 11-13 mg / m³. 3 ;

[0063] (3) The OMR membrane provided by this invention has no risk of delamination; after 96h of UV aging test, it shows no yellowing (yellowing index ΔYI is 1.1-1.3) and no texture deformation; the difference in thermal expansion coefficient between the inner texture layer and the outer texture sub-mold layer is ≤5×10 -5 / ℃, can withstand high and low temperature cycling tests from -40℃ to 85℃ (no cracking or deformation after 50 cycles);

[0064] (4) When the OMR film provided by the present invention is used in the back cover of a mobile phone, the back cover of the mobile phone has no visible particles, good texture consistency, meets the appearance standards of high-end mobile phones, and can improve the durability and yield of the back cover of the mobile phone. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the structure of the OMR membrane provided in Example 1;

[0066] Among them, 1-substrate layer, 2-outer texture master mold layer, 3-outer texture sub-mold layer, 4-inner texture layer, 5-coating layer, and 6-ink layer. Detailed Implementation

[0067] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be considered as specific limitations thereof.

[0068] The sources of some components in the following examples and comparative examples are as follows:

[0069] (1) PET film: Toray PET A4300, light transmittance 92%, thickness 0.1mm;

[0070] (2) Polyurethane acrylate UV adhesive

[0071] Polyurethane acrylate UV adhesive-1, Huizhou Deyouwei New Material Co., Ltd., 3361-WG0558;

[0072] Polyurethane acrylate UV adhesive-2, Huizhou Deyouwei New Material Co., Ltd., 3361-WG0655, its components include a first polyurethane acrylate photosensitive resin, a first initiator, a first monomer, and additives; based on the mass of the first polyurethane acrylate photosensitive resin as 100%, the first initiator is 5%, the first monomer is 30%, and the additives are 5%;

[0073] Polyurethane acrylate UV adhesive-3, Huizhou Deyouwei New Material Co., Ltd., 3361-WG0579, its components include a second polyurethane acrylate photosensitive resin, a second initiator, a second monomer and 1,6-hexanediol diacrylate, the amount of each component can be adjusted by the user;

[0074] (3) Black polyurethane ink: purchased from Dolby Ink DB-880, VOC content ≤5%;

[0075] (4) Bridging varnish: Shenzhen Jiabeida Technology Co., Ltd., W08;

[0076] (5) UV master mold adhesive: Shenzhen Jiabeida Technology Co., Ltd., A66-216B;

[0077] (6) UV mold adhesive: Shenzhen Jiabeida Technology Co., Ltd., S-2161-1;

[0078] (7) UV internal texture adhesive: Shenzhen Jiabeida Technology Co., Ltd., N-6088.

[0079] Example 1

[0080] An OMR membrane, the structural schematic diagram of which is shown below. Figure 1 As shown, the OMR film includes a substrate layer 1, an outer texture master mold layer 2, an outer texture sub-mold layer 3, an inner texture layer 4, a coating layer 5, and an ink layer 6, which are stacked sequentially. The preparation method of the OMR film includes the following steps:

[0081] (1) Remove surface impurities from the PET film using a plasma cleaner (500W power, 30s processing time). Apply polyurethane acrylate UV adhesive-1 to the PET film using a UV transfer machine. Roll press the film into a wet film with a thickness of 10μm. Then cure the film with ultraviolet light (wavelength 395nm, LED energy 2000mJ / cm). 2 (Exposure time 10s) curing, forming an outer texture master mold layer;

[0082] (2) Apply polyurethane acrylate UV adhesive-2 to the surface of the outer texture master mold layer away from the PET film using the same UV transfer printing machine, roll it into a wet film with a thickness of 15μm, and cure it by ultraviolet light (LED energy 450mJ / cm). 2 An outer textured sub-mold layer is formed by an exposure time of 20 seconds, with a UV blocking rate of 92%.

[0083] (3) 100 parts by weight of the second polyurethane acrylate photosensitive resin, 5 parts by weight of the second initiator, 20 parts by weight of the second monomer and 10 parts by weight of 1,6-hexanediol diacrylate were stirred evenly at a stirring speed of 500 r / min for 30 min to obtain polyurethane acrylate UV adhesive-3; the polyurethane acrylate UV adhesive-3 was transferred to the surface of the outer texture sub-mold layer away from the outer texture master mold layer by a UV transfer machine, rolled into a wet film with a thickness of 10 μm, and then cured with ultraviolet light (LED energy 1000 mJ / cm). 2 An inner texture layer is formed by an exposure time of 15 seconds. The inner texture layer, the outer texture sub-mold layer, and the outer texture master layer are all free of bubbles and do not exhibit any delamination.

[0084] (4) Place the above-mentioned film into a vacuum coating machine (vacuum degree 5×10). -3 Pa, evaporation current 100A), SiO2 is evaporated on the surface of the inner texture layer away from the outer texture sub-mold layer to form a coating layer with a thickness of 300nm;

[0085] Black polyurethane ink was screen printed on the surface of the coating layer away from the inner texture layer using a screen printing machine (400 mesh) to form a wet film with a thickness of 8 μm. The film was then placed in an oven (80°C, 30 min) to dry and cure. The screen printing was repeated 3 times to form an ink layer with a thickness of 24 μm, thus obtaining the OMR film.

[0086] Example 2

[0087] An OMR film, comprising a substrate layer, an outer texture master layer, an outer texture sub-mold layer, an inner texture layer, a coating layer, and an ink layer stacked sequentially; the preparation method of the OMR film includes the following steps:

[0088] (1) Remove surface impurities from the PET film using a plasma cleaner (500W power, 30s processing time). Apply polyurethane acrylate UV adhesive-1 to the PET film using a UV transfer machine. Roll press the film into a wet film with a thickness of 10μm. Then cure the film with ultraviolet light (wavelength 395nm, LED energy 2300mJ / cm²). 2 (Exposure time 10s) curing, forming an outer texture master mold layer;

[0089] (2) Apply polyurethane acrylate UV adhesive-2 to the surface of the outer texture master mold layer away from the PET film using the same UV transfer printing machine, roll it into a wet film with a thickness of 15μm, and cure it by ultraviolet light (LED energy 430mJ / cm). 2 An outer textured sub-mold layer is formed by an exposure time of 20 seconds, with a UV blocking rate of 92%.

[0090] (3) 100 parts by weight of the second polyurethane acrylate photosensitive resin, 5 parts by weight of the second initiator, 18 parts by weight of the second monomer, and 8 parts by weight of 1,6-hexanediol diacrylate were stirred evenly at a stirring speed of 500 r / min for 30 min to obtain polyurethane acrylate UV adhesive-3; the polyurethane acrylate UV adhesive-3 was transferred to the surface of the outer texture sub-mold layer away from the outer texture master mold layer using a UV transfer machine, rolled into a wet film with a thickness of 10 μm, and then cured with ultraviolet light (LED energy 800 mJ / cm). 2 An inner texture layer is formed by an exposure time of 15 seconds. The inner texture layer, the outer texture sub-mold layer, and the outer texture master layer are all free of bubbles and do not exhibit any delamination.

[0091] (4) Place the above-mentioned film into a vacuum coating machine (vacuum degree 5×10). -3 (Pa, evaporation current 100A), TiO2 is evaporated on the surface of the inner texture layer away from the outer texture sub-mold layer to form a coating layer with a thickness of 300nm;

[0092] Black polyurethane ink was screen printed on the surface of the coating layer away from the inner texture layer using a screen printing machine (400 mesh) to form a wet film with a thickness of 8 μm. The film was then placed in an oven (80°C, 30 min) to dry and cure. The screen printing was repeated 3 times to form an ink layer with a thickness of 24 μm, thus obtaining the OMR film.

[0093] Example 3

[0094] An OMR film and its preparation method are different from those in Example 1. The only difference is that in step (3) polyurethane acrylate UV adhesive-3, the second polyurethane acrylate photosensitive resin is 100 parts by weight, the second initiator is 5 parts by weight, the second monomer is 10 parts by weight, and 1,6-hexanediol diacrylate is 5 parts by weight. The other raw materials, process parameters and steps are the same as those in Example 1.

[0095] Example 4

[0096] An OMR film and its preparation method are different from those in Example 1. The only difference is that in step (3) of polyurethane acrylate UV adhesive-3, the second polyurethane acrylate photosensitive resin is 100 parts by weight, the second initiator is 5 parts by weight, the second monomer is 20 parts by weight, and 1,6-hexanediol diacrylate is 5 parts by weight. The other raw materials, process parameters and steps are the same as those in Example 1.

[0097] Example 5

[0098] An OMR film and its preparation method are different from those in Example 1. The only difference is that in step (3) polyurethane acrylate UV adhesive-3, the second polyurethane acrylate photosensitive resin is 100 parts by weight, the second initiator is 5 parts by weight, the second monomer is 20 parts by weight, and 1,6-hexanediol diacrylate is 8 parts by weight. The other raw materials, process parameters and steps are the same as those in Example 1.

[0099] Comparative Example 1

[0100] An OMR film, comprising a substrate layer, an outer texture master layer, an outer texture sub-mold layer, a crosslinking varnish layer, an inner texture layer, a coating layer, and an ink layer stacked sequentially; the preparation method of the OMR film includes the following steps:

[0101] (1) Remove surface impurities from the PET film using a plasma cleaner (500W power, 30s processing time). Apply UV mastering adhesive A66-216B to the PET film using a UV transfer machine. Roll press the film into a wet film with a thickness of 10μm. Then cure the film with a UV light (wavelength 395nm, LED energy 1000mJ / cm²). 2 (Exposure time 10s) curing, forming an outer texture master mold layer;

[0102] (2) Apply UV sub-molding adhesive S-2161-1 to the surface of the outer texture master mold layer away from the PET film using the same UV transfer printing machine, roll it into a wet film with a thickness of 15μm, and cure it by ultraviolet light (LED energy 500mJ / cm). 2 An outer textured sub-mold layer is formed by an exposure time of 20 seconds, with a UV blocking rate of 91%.

[0103] (3) The cross-linking varnish W08 is screen printed on the surface of the outer texture sub-mold layer away from the outer texture master mold layer using a 300-mesh screen printing plate on a printing equipment. Then it is placed in an oven at 85°C for 30 minutes to complete the curing and form a cross-linking varnish layer with a thickness of 10μm.

[0104] (4) The UV internal texture adhesive N-6088 is transferred to the surface of the crosslinking varnish layer away from the external texture sub-mold layer using a UV transfer machine, rolled into a wet film with a thickness of 10μm, and then cured with ultraviolet light (LED energy 800mJ / cm). 2 An inner texture layer is formed by an exposure time of 15 seconds. The inner texture layer, the bridging varnish layer, the outer texture sub-mold layer, and the outer texture master mold layer are all free of bubbles and do not exhibit delamination.

[0105] (5) Place the above-mentioned film into a vacuum coating machine (vacuum degree 5×10). -3 Pa, evaporation current 100A), SiO2 is evaporated on the surface of the inner texture layer away from the outer texture sub-mold layer to form a coating layer with a thickness of 300nm;

[0106] Black polyurethane ink was screen printed on the surface of the coating layer away from the inner texture layer using a screen printing machine (400 mesh) to form a wet film with a thickness of 8 μm. The film was then placed in an oven (80°C, 30 min) to dry and cure. The screen printing was repeated 3 times to form an ink layer with a thickness of 24 μm, thus obtaining the OMR film.

[0107] Performance testing

[0108] (1) Appearance defect rate: Visual inspection (200mm distance) shows that the appearance of particles, orange peel and wrinkles is considered to be defective. 1000 pieces are sampled, the number of OMR membranes with appearance defects is counted, and the proportion of OMR membranes with appearance defects is calculated, which is the appearance defect rate.

[0109] (2) Yellowing index ΔYI: Tested according to GB / T 16422.3-2022, test duration 96h;

[0110] (3) High and low temperature cycling performance: Tested according to GB / T 2423.22-2012, test conditions -40℃ (2h) ~ 85℃ (2h), 50 cycles;

[0111] (4) VOC emissions: tested according to GB 30981-2022;

[0112] (5) Surface hardness: According to GB / T 6739-2022, use a test pencil lead with specified hardness (pencil hardness is 2H), apply a pressure of 1 kgf, and make 5 strokes at the test position with the pencil lead and the angle between the pencil lead and the surface of the sample to be tested being 45°. Each stroke is 5~10 mm long. If no trace is left after erasing with an eraser after the test, the test is considered to have passed.

[0113] (6) Adhesion between the inner texture layer and the outer texture sub-mold layer after boiling: After boiling in water at 98℃ for 2 hours, wipe off the moisture and conduct a cross-cut test according to GB / T 9286-2021. Visually inspect whether the outer texture sub-mold layer has fallen off. If it has fallen off and the area of ​​fall-off is ≤15%, it is recorded as slight fall-off.

[0114] The OMR membranes provided in the examples and comparative examples were tested according to the above method, and the test results are shown in Table 1:

[0115] Table 1

[0116]

[0117] As can be seen from the test data in Table 1, the OMR membrane provided by this invention has a low appearance defect rate, strong adhesion between the inner and outer layers after boiling in water, excellent mechanical properties and aging resistance, and low VOC emissions.

[0118] As can be seen from the comparison between Example 1 and Comparative Example 1, the appearance defect rate increases significantly after adding the crosslinking varnish layer. This is because the crosslinking varnish requires a high level of environmental cleanliness when screen printing, which easily leads to defects such as particulate spots, greatly affecting the overall yield of the membrane and increasing the production process and production cost. At the same time, the use of crosslinking varnish increases VOC emissions, further polluting the environment. In contrast, the OMR membrane provided by this invention has less impact on the overall performance of the OMR membrane after eliminating the crosslinking varnish layer, and the appearance defect rate and VOC emissions are significantly reduced.

[0119] The applicant declares that the OMR membrane, its preparation method, and its application are illustrated through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An OMR membrane, characterized in that, The OMR film comprises a substrate layer, an outer texture master layer, an outer texture sub-mold layer, and an inner texture layer, which are stacked sequentially. The raw materials for preparing the outer textured sub-mold layer include a first polyurethane acrylate UV adhesive; The raw materials for preparing the inner texture layer include a second polyurethane acrylate UV adhesive; the components of the second polyurethane acrylate UV adhesive include multifunctional acrylate additives.

2. The OMR membrane according to claim 1, characterized in that, The material of the substrate layer includes any one or a combination of at least two of polyethylene terephthalate, polycarbonate or polyolefin; The thickness of the substrate layer is 0.1-0.3 mm.

3. The OMR membrane according to claim 1, characterized in that, The thickness of the outer texture master mold layer is 10-15 μm; The raw materials for preparing the outer texture master mold layer include a third type of polyurethane acrylate UV adhesive; The tensile strength of the third polyurethane acrylate UV adhesive after curing is 10-20 MPa.

4. The OMR membrane according to claim 1, characterized in that, The thickness of the outer textured sub-mold layer is 15-20 μm; The components of the first polyurethane acrylate UV adhesive include a first polyurethane acrylate photosensitive resin, a first initiator, a first monomer, and additives; Based on the mass of the first polyurethane acrylate photosensitive resin being 100%, the mass of the first initiator is 5-8%, the mass of the first monomer is 25-30%, and the mass of the additives is 5-10%. The UV blocking rate of the outer textured sub-mold layer is ≥90%.

5. The OMR membrane according to claim 1, characterized in that, The second polyurethane acrylate UV adhesive also includes a second polyurethane acrylate photosensitive resin, a second initiator, and a second monomer. The multifunctional acrylate additives include 1,6-hexanediol diacrylate; Based on the mass of the second polyurethane acrylate photosensitive resin being 100%, the mass of the second initiator is 1-5%, the mass of the second monomer is 10-20%, and the mass of the multifunctional acrylate additive is 5-10%. The thickness of the inner texture layer is 8-15 μm.

6. The OMR membrane according to claim 1, characterized in that, The OMR membrane further includes a functional layer; the functional layer is disposed on the surface of the inner texture layer away from the outer texture sub-mold layer; The functional layer includes a coating layer and an ink layer stacked together; the coating layer is located near the inner texture layer and away from the outer texture sub-mold layer. The thickness of the coating layer is 0.1-0.4 μm; The material of the coating layer includes any one or a combination of at least two of SiO2, TiO2 or ZrO2; The thickness of the ink layer is 10-25 μm; The material of the ink layer includes black polyurethane ink.

7. A method for preparing an OMR membrane as described in any one of claims 1-6, characterized in that, The preparation method includes: The OMR film is obtained by sequentially stacking a substrate layer, an outer texture master layer, an outer texture sub-mold layer, and an inner texture layer.

8. The preparation method according to claim 7, characterized in that, The preparation method specifically includes the following steps: (1) The raw material for preparing the outer texture master mold layer is transferred onto one surface of the substrate layer and then cured to form the outer texture master mold layer; (2) The raw material for preparing the outer texture sub-mold layer is transferred onto the surface of the outer texture master mold layer away from the substrate layer, and then cured to form the outer texture sub-mold layer; (3) The raw material for preparing the inner texture layer is transferred onto the surface of the outer texture sub-mold layer away from the outer texture master mold layer, and then cured to form the inner texture layer, thus obtaining the OMR film.

9. The preparation method according to claim 8, characterized in that, The curing process in step (1) is completed by ultraviolet light irradiation, with a light energy of 2000-3000 mJ / cm². 2 The exposure time is 8-12 seconds; The curing process in step (2) is completed by ultraviolet light irradiation, with a light energy of 300-500 mJ / cm. 2 The exposure time is 20-30 seconds; The curing process in step (3) is completed by ultraviolet light irradiation, with a light energy of 800-1300 mJ / cm². 2 The exposure time is 10-20 seconds; After the curing is completed in step (3), a functional layer is also provided on the surface of the inner texture layer away from the outer texture sub-mold layer.

10. An application of an OMR membrane as described in any one of claims 1-6 in a mobile phone, tablet computer, or laptop computer.

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