A kind of under-screen fingerprint optical unlocking screen protective film and preparation method thereof

Abstract

The present invention provides an under-screen fingerprint optical unlocking screen protective film and a preparation method thereof, wherein the protective film comprises a hardened coating, a cellulose diacetate film layer, a pressure-sensitive adhesive layer and a release film layer which are in contact with each other in sequence. The protective film provided by the present invention uses a cellulose diacetate film layer as a base film, which is compounded with other layers, so that the protective film has zero phase difference, a light transmittance of >90%, a haze of <3%, and a high response sensitivity to the under-screen optical recognition system; good stiffness, and a tensile strength of >80N / mm 2 , will not leave indentations on the optical screen protective film; high hardness, >2H (500g), good wear resistance, >1000 times (#0000 steel wool, 1kg); small surface friction, dynamic friction coefficient <0.1; can be hot-bent, and the forming surface has high precision, and can fit large curved screens without warping; biodegradable and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of screen protective films, and in particular relates to an under-screen fingerprint optical unlocking screen protective film and a preparation method thereof. Background Art

[0002] In addition to biometric technologies such as iris recognition, vein recognition, and face recognition, fingerprint recognition technology is one of the most mainstream biometric methods currently used in mobile terminals. With the popularity of full-screen phones, traditional fingerprint unlocking, such as front unlocking or back unlocking, requires a fingerprint collection window, which will inevitably affect the screen-to-body ratio of the full-screen phone, and thus affect the appearance of smart devices such as mobile phones. Therefore, under-screen fingerprint recognition technology came into being. The current under-screen fingerprint recognition technology mainly uses two methods: under-screen fingerprint optical recognition and under-screen fingerprint ultrasonic recognition. Under-screen fingerprint ultrasonic recognition technology is maturely used by Samsung in mass-produced mobile phone models, while under-screen fingerprint optical recognition technology is a mainstream technology maturely used by major domestic brands such as Huawei, OPPO, VIVO, and Xiaomi.

[0003] The principle of the under-screen fingerprint optical recognition technology is: when the user's finger presses the OLED screen, the light emitted by the OLED screen illuminates the finger fingerprint area, and the reflected light that illuminates the finger fingerprint returns to the sensor under the screen through the gaps between the pixels of the OLED screen. The final fingerprint image is compared and analyzed with the fingerprint images stored in the database, and the screen is unlocked after a matching identification is made.

[0004] The base film used for screen protectors is generally a transparent optical film. Usually, polymer optical films are prepared by unidirectional or bidirectional stretching after melt extrusion, because unidirectional or bidirectional stretching process can improve the comprehensive properties of optical films such as mechanical strength. However, the stretching process will inevitably lead to the anisotropy of the optical film, which in turn leads to the generation of birefringence. The birefringence phenomenon will cause phase difference when light passes through the film, which will greatly affect the path of light and change the characteristics of light, and will cause the optical information reflected to the under-screen fingerprint optical sensor to be disordered, and the correct fingerprint information cannot be obtained, resulting in delays or even failures in the optical recognition of fingerprints under the screen. In contrast, if the phase difference of the optical film is zero, the light will not be affected by the path and the characteristics will not change when passing through the film, and will not cause delays and failures in the optical recognition of fingerprints under the screen, so as to meet the requirements of the base film of the under-screen fingerprint optical unlocking screen protector.

[0005] Currently, the film substrates on the market that do not affect the optical unlocking of under-screen fingerprints mainly include polycarbonate (PC) film, cellulose triacetate (TAC) film, thermoplastic polyurethane (TPU) film and TOYOBO's super-reflective polyester (PET) film "COSMOSHINE "Among them, the surface of polycarbonate film is difficult to harden and scratch-resistant, triacetate cellulose film has poor high temperature and humidity resistance, and thermoplastic polyurethane film has poor stiffness and easily leaves indentations on the optical screen protective film. None of them have been successfully applied to under-screen optical fingerprint unlocking screen protective films.

[0006] Therefore, developing an optical screen protector with zero phase difference, which can fit large curved screens without warping and is suitable for under-screen fingerprint optical unlocking systems, is a technical challenge that needs to be solved urgently. Summary of the invention

[0007] In view of this, the object of the present invention is to provide an under-screen fingerprint optical unlocking screen protective film and a preparation method thereof. The screen protective film has zero phase difference (meaning the phase difference is very low, close to zero), and can fit a large curved screen without warping.

[0008] The present invention provides an under-screen fingerprint optical unlocking screen protective film, comprising a hardened coating layer, a cellulose diacetate film layer, a pressure-sensitive adhesive layer and a release film layer which are in contact with each other in sequence.

[0009] Preferably, the thickness of the cellulose diacetate film layer is 14-500 μm, the thickness of the hardening coating layer is 1-10 μm, and the thickness of the pressure-sensitive adhesive layer is 20-80 μm.

[0010] Preferably, the cellulose diacetate film layer has a light transmittance of >90%, a haze of <3%, zero phase difference, and a tensile strength of >80 N / mm 2 .

[0011] Preferably, the hardened coating is an acrylic coating with an elongation at break > 150% and a dynamic friction coefficient < 0.1.

[0012] Preferably, a protective film layer is attached to the surface of the hardened coating.

[0013] Preferably, the peeling force of the pressure-sensitive adhesive layer on the anti-fingerprint coated glass is greater than 15gf / 25mm.

[0014] Preferably, an optical grade thermoplastic polyurethane (TPU) film layer may be disposed between the cellulose diacetate film layer and the pressure-sensitive adhesive layer.

[0015] The present invention provides a method for preparing the under-screen fingerprint optical unlocking screen protective film described in the above technical solution, comprising the following steps:

[0016] The hardening coating liquid is applied on the cellulose diacetate film, and then dried and cured by ultraviolet light to obtain a hardening coating-cellulose diacetate film composite layer;

[0017] A pressure-sensitive adhesive is applied on the surface of the cellulose diacetate film of the hardened coating-cellulose diacetate film composite layer and then a release film is attached or a pressure-sensitive adhesive with a release film is directly attached to obtain an under-screen fingerprint optical unlocking screen protective film;

[0018] Preferably, the under-screen fingerprint optical unlocking screen protective film is further hot-bent to obtain a curved under-screen fingerprint optical unlocking screen protective film.

[0019] Or the cellulose diacetate film is heat-bent into shape and then cooled;

[0020] The hardening coating liquid is applied on the cellulose diacetate film, and then dried and cured by ultraviolet light to obtain a hardening coating-cellulose diacetate film composite layer;

[0021] A pressure-sensitive adhesive with a release film is adhered to the surface of the cellulose diacetate film of the hardened coating-cellulose diacetate film composite layer to obtain an under-screen fingerprint optical unlocking screen protective film.

[0022] Preferably, the temperature of the hot bending forming is greater than 200°C.

[0023] Preferably, the hardening coating liquid is selected from Japanese Shin-Etsu SY-5211 or Dongguan Beiteli BTF-220.

[0024] Preferably, the drying temperature is 75-125°C, the drying time is 4-6 minutes; the curing is ultraviolet curing, and the ultraviolet energy is 280-620 mJ / cm 2 .

[0025] The present invention provides an under-screen fingerprint optical unlocking screen protective film, comprising a hardened coating, a cellulose diacetate film layer, a pressure-sensitive adhesive layer and a release film layer in contact with each other in sequence. The protective film provided by the present invention uses a cellulose diacetate film layer as a base film, which is compounded with other layers, so that the protective film has zero phase difference, a light transmittance of >90%, a haze of <3%, and a high response sensitivity to the under-screen optical recognition system; good stiffness, and a tensile strength of >80N / mm 2, will not leave indentations on the optical screen protective film; high hardness, >2H (500g), good wear resistance, >1000 times (#0000 steel wool, 1kg); small surface friction, dynamic friction coefficient <0.1; can be hot-bent, and the forming surface has high precision, and can fit large curved screens without warping; biodegradable and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the structure of the under-screen fingerprint optical unlocking screen protective film provided by the present invention. DETAILED DESCRIPTION

[0027] The present invention provides an under-screen fingerprint optical unlocking screen protective film, comprising a hardened coating layer, a cellulose diacetate film layer, a pressure-sensitive adhesive layer and a release film layer which are in contact with each other in sequence.

[0028] The protective film provided by the present invention uses a cellulose diacetate film layer as a base film, which is compounded with other layers, so that the protective film has zero phase difference, light transmittance>90%, haze<3%, and high response sensitivity to the optical recognition system under the screen; good stiffness, tensile strength>80Nmm -2 , will not leave indentations on the optical screen protective film; high hardness, >2H (500g), good wear resistance, >1000 times (#0000 steel wool, 1kg); small surface friction, dynamic friction coefficient <0.1; can be hot-bent, and the forming surface has high precision, and can fit large curved screens without warping; biodegradable and environmentally friendly.

[0029] See also Figure 1 , Figure 1 This is a schematic structural diagram of the under-screen fingerprint optical unlocking screen protective film provided by the present invention; wherein 1 is a protective film layer (optional), 2 is a hardened coating layer, 3 is a cellulose diacetate film layer, 4 is a pressure-sensitive adhesive layer and 5 is a release film layer.

[0030] The under-screen fingerprint optical unlocking screen protective film provided by the present invention preferably includes a protective film layer 1; the protective film layer mainly protects the screen protective film from unnecessary damage during production and transportation. The protective film requires no residual glue and no ghosting when removed. The protective film layer is preferably selected from one of the commercially available acrylic protective film, silicone protective film and polyurethane protective film, more preferably an acrylic protective film. The thickness of the protective film is preferably 20 to 200 μm. In a specific embodiment, the protective film is selected from Shenzhen Bo Chuangda ST36065L or Dongguan Wenle WL003.

[0031] The under-screen fingerprint optical unlocking screen protective film provided by the present invention includes a hardened coating 2 in contact with the protective film layer. The hardness of the hardened coating is preferably >2H (500g); the wear resistance is preferably >1000 times (#0000 steel wool, 1kg); the surface friction force is preferably a dynamic friction coefficient <0.1. The hardened coating is preferably prepared by coating with a hardening coating liquid, and more preferably by coating with an acrylic paint. The thickness of the hardened coating is preferably 1 to 10 μm, and more preferably 3 to 8 μm. In a specific embodiment, the hardening coating liquid is selected from Japan Shin-Etsu SY-5211 and / or Dongguan Beiteli BTF-220. The thickness of the hardened coating is 3 μm, the hardness is 3H, and the adhesion is 5B.

[0032] The under-screen fingerprint optical unlocking screen protective film provided by the present invention includes a transparent cellulose diacetate film layer 3 in contact with the hardened coating. The thickness of the cellulose diacetate film layer is preferably 14 to 500 μm, more preferably 30 to 300 μm, and most preferably 40 to 150 μm. In a specific embodiment, the thickness of the transparent cellulose diacetate film layer is 50 μm, 75 μm, 100 μm or 125 μm cellulose diacetate, specifically a cellulose diacetate film of model Celanese Clarifoil.

[0033] In the present invention, the cellulose diacetate film layer has a light transmittance of >90%, a haze of <3%, a zero phase difference, and a tensile strength of >80N / mm 2 . The surface of the cellulose diacetate film layer is easy to harden and scratch-resistant, has good adhesion to optical-grade pressure-sensitive adhesives, and has a surface energy of >38dyn / cm, which is very suitable as a base film for the under-screen fingerprint optical unlocking screen protective film. More importantly, the cellulose diacetate film has excellent thermoplasticity, and can be used to prepare an optical screen protective film that meets the needs of large-curved curved screens through hot bending. The molded curved surface has high precision and can fit the large-curved curved screen without warping. At the same time, the cellulose diacetate film itself is a biodegradable, environmentally friendly material that meets the requirements of green environmental protection. The degree of esterification of the cellulose diacetate film is preferably 2.28 to 2.49, and it has hot-bendable properties. The molecular formula of the cellulose acetate is [C6H7O2(OCOCH3)X(OH)3-X]n, n=200 to 400. When the esterification degree X = 2.28-2.49 (equivalent to acetic acid content 53%-56%), it is diacetate cellulose, and its acetyl content is 38%-40%. When the esterification degree X>2.7 (equivalent to acetic acid content>59%), it is triacetate cellulose (TAC), and its acetyl content is>45%.

[0034] Table 1 Properties of cellulose acetate at different degrees of esterification

[0035]

[0036] The under-screen fingerprint optical unlocking screen protective film provided by the present invention includes a pressure-sensitive adhesive layer 4 in contact with the diacetyl cellulose film. The pressure-sensitive adhesive layer is used to bond with the screen surface glass. The peeling force of the pressure-sensitive adhesive layer on the anti-fingerprint coated glass is >15gf / 25mm. The pressure-sensitive adhesive layer is preferably selected from one of an acrylate pressure-sensitive adhesive, a silicone pressure-sensitive adhesive or a polyurethane pressure-sensitive adhesive. The thickness of the pressure-sensitive adhesive layer is preferably 20 to 80μm. The pressure-sensitive adhesive used in the pressure-sensitive adhesive layer is specifically Taiwan Changxing Chemical 7712G or the United States Dow-Corning 7657.

[0037] The under-screen fingerprint optical unlocking screen protective film provided by the present invention includes a release film layer 5 in contact with the pressure-sensitive adhesive layer. The release film layer mainly protects the pressure-sensitive adhesive layer and can be a commercially available ordinary release film. The thickness of the release film layer is preferably 20 to 100 μm. In a specific embodiment of the present invention, the release film layer is Dongguan Yuancai F5070 or Shenzhen Degussaino 2330A03.

[0038] In the under-screen fingerprint optical unlocking screen protective film provided by the present invention, an optical grade thermoplastic polyurethane (TPU) film layer may be preferably provided between the diacetate cellulose film layer and the pressure-sensitive adhesive layer. The optical grade thermoplastic polyurethane film layer may be compounded or coated between the diacetate cellulose film layer and the pressure-sensitive adhesive layer. The thermoplastic polyurethane film serves to increase the overall flexibility of the protective film, and has better conformability and anti-warping performance in the application of curved screens.

[0039] Preferably, the optical grade thermoplastic polyurethane film layer has a thickness of 10-500 μm, an elongation at break of >200%, and a haze of <3%. In a specific embodiment of the present invention, the thermoplastic polyurethane film is Japanese Seiden DUS6056WPET with a thickness of 100 μm.

[0040] The present invention provides a method for preparing the under-screen fingerprint optical unlocking screen protective film described in the above technical solution, comprising the following steps:

[0041] The hardening coating liquid is applied on the cellulose diacetate film, and then dried and cured by ultraviolet light to obtain a hardening coating-cellulose diacetate film composite layer;

[0042] The hardened coating surface of the hardened coating-cellulose diacetate film composite layer is adhered to a protective film, and the surface of the cellulose diacetate film layer is coated with a pressure-sensitive adhesive and then adhered to a release film or directly adhered to a pressure-sensitive adhesive with a release film to obtain an under-screen fingerprint optical unlocking screen protective film.

[0043] In the present invention, the under-screen fingerprint optical unlocking screen protective film is preferably further hot-bent to obtain a curved under-screen fingerprint optical unlocking screen protective film.

[0044] Or the present invention prepares the under-screen fingerprint optical unlocking screen protective film according to the following method:

[0045] The cellulose diacetate film is heat-bent into shape and then cooled;

[0046] The hardening coating liquid is applied on the cellulose diacetate film, and then dried and cured by ultraviolet light to obtain a hardening coating-cellulose diacetate film composite layer;

[0047] A pressure-sensitive adhesive with a release film is adhered to the surface of the cellulose diacetate film of the hardened coating-cellulose diacetate film composite layer to obtain an under-screen fingerprint optical unlocking screen protective film.

[0048] Preferably, an optical grade thermoplastic polyurethane film layer is further compounded or coated between the diacetate cellulose film layer and the pressure-sensitive adhesive layer. The optical grade thermoplastic polyurethane film layer may have one layer or multiple layers. In a specific embodiment, the optical grade thermoplastic polyurethane film layer is compounded on the diacetate cellulose film layer.

[0049] The temperature of the hot bending molding is preferably greater than 200°C. In the present invention, the drying is preferably carried out in an oven known to those skilled in the art; the drying temperature is preferably 75-125°C, and the drying time is 4-6 minutes; in a specific embodiment, the drying temperature is 80°C and the time is 5 minutes. The energy of UV curing is preferably 280-620 mJ / cm 2 In a specific embodiment, the energy of UV curing is 400mJ / cm 2 .

[0050] The method provided by the invention is simple and easy to industrialize.

[0051] The present invention tests the performance of the under-screen fingerprint optical unlocking screen protective film according to the following test methods: the test method for light transmittance and haze is ASTM D1003; the test method for hardness is ASTM D3363 (500g); the test method for wear resistance is ASTM D4060 (#0000 steel wool, 1Kg); the test method for rainbow pattern and polarization angle adopts the light meter method; the test method for tensile strength and breaking strength is ASTM D 882; the test method for the curvature 88° screen fit uses a real machine to fit the protective film to check its fit.

[0052] In order to further illustrate the present invention, an under-screen fingerprint optical unlocking screen protective film and a preparation method thereof provided by the present invention are described in detail below in combination with embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] First, the hardening coating liquid (Japanese Shin-Etsu SY-5211) was coated on a 50 μm thick cellulose diacetate base film layer of Celanese Clarifoil, and then dried in an oven at 80°C for 5 minutes; then cured by ultraviolet light with a UV energy of 400 mJ / cm 2 ; A hardened coating is formed with a thickness of 3μm, a hardness of 3H, and an adhesion of 5B. A common protective film (Shenzhen Bo Chuangda ST36065L) is attached. A pressure-sensitive adhesive (US Dow-Corning 7657) is applied on the other side of the hardened cellulose diacetate film and dried and cured. A release film (Dongguan Yuancai F5070) is attached to obtain an under-screen fingerprint optical unlocking screen protective film.

[0055] Example 2

[0056] First, the hardening coating liquid (Japanese Shin-Etsu SY-5211) was coated on a 75 μm thick Celanese Clarifoil diacetate cellulose base film layer, and then dried in an oven at 80°C for 5 minutes; then cured by ultraviolet light with a UV energy of 400 mJ / cm 2 ; Form a hardened coating with a thickness of 3μm, a hardness of 3H, and an adhesion of 5B. Apply a common protective film (Shenzhen Bo Chuangda ST36065L). Apply a pressure-sensitive adhesive (Dow-Corning 7657, USA) on the other side of the hardened cellulose diacetate film and dry and solidify. Apply a release film (Dongguan Yuancai F5070). Use a hot press >200℃ to bend and shape to obtain a curved screen fingerprint optical unlocking screen protective film.

[0057] Example 3

[0058] First, the hardening coating liquid (Dongguan Beiteli BTF-220) was coated on a 50μm thick Celanese Clarifoil diacetate cellulose base film layer, and then dried in an oven at 80°C for 5 minutes; then cured by ultraviolet light with a UV energy of 400mJ / cm 2; A hardened coating is formed with a thickness of 3μm, a hardness of 3H, and an adhesion of 5B. A common protective film (Wenle WL003, Dongguan) is attached. A pressure-sensitive adhesive (Changxing Chemical 7712G, Taiwan, China) is applied on the other side of the hardened cellulose diacetate film and dried and cured. A release film (Degusano 2330A03, Shenzhen) is attached to obtain an under-screen fingerprint optical unlocking screen protective film.

[0059] Example 4

[0060] First, the hardening coating liquid (Dongguan Beiteli BTF-220) was coated on a 75μm thick cellulose diacetate base film layer of Celanese Clarifoil, and then dried in an oven at 80°C for 5 minutes; then cured by ultraviolet light with a UV energy of 400mJ / cm 2 ; Form a hardened coating with a thickness of 3μm, a hardness of 3H, and an adhesion of 5B. Apply a common protective film (Wenle WL003, Dongguan). Apply a pressure-sensitive adhesive (Changxing Chemical 7712G, Taiwan, China) on the other side of the hardened cellulose diacetate film and dry and solidify. Apply a release film (Degussaino 2330A03, Shenzhen). Use a hot press >200℃ to bend and form to obtain a curved screen fingerprint optical unlocking screen protective film.

[0061] Example 5

[0062] First, a hot press machine was used to bend the cellulose acetate film at 200°C and then cooled. A hardening coating liquid (BTF-220 from Dongguan Bettery) was applied to the 50μm thick Celanese Clarifoil cellulose acetate film that was bend and dried in an oven at 80°C for 5 minutes. The film was then cured by UV irradiation at 400mJ / cm 2 ; A hardened coating is formed with a thickness of 3μm, a hardness of 3H, and an adhesion of 5B. A common protective film (Wenle WL003, Dongguan) is attached. A coated pressure-sensitive adhesive (Changxing Chemical 7712G, Taiwan, China) is attached to the other side of the hot-bent and hardened cellulose acetate film. A release film (Degusano 2330A03, Shenzhen) is attached to obtain a curved screen fingerprint optical unlocking screen protective film.

[0063] Example 6

[0064] First, a 50μm thick Celanese Clarifoil diacetate cellulose base film layer was composited with a 100μm thermoplastic polyurethane film (Japan Seiden DUS6056WPET). Then a hardening coating liquid (Dongguan Beiteli BTF-220) was applied to the diacetate cellulose base film surface of the composite film, and then dried in an oven at 80°C for 5 minutes; then cured by UV light with a UV energy of 400mJ / cm 2 ; Form a hardened coating with a thickness of 3μm, a hardness of 3H, and an adhesion of 5B. Apply a common protective film (Wenle WL003, Dongguan). Apply a pressure-sensitive adhesive (Changxing Chemical 7712G, Taiwan, China) on the thermoplastic polyurethane surface of the hardened composite film and dry and solidify. Apply a release film (Degussaino 2330A03, Shenzhen). Use a hot press >200℃ to bend and form to obtain a curved screen fingerprint optical unlocking screen protective film.

[0065] Comparative Example 1

[0066] Comparative Example 1 is substantially the same as Example 1, except that the base film material used is a commercially available triacetate cellulose film (Dongguan Meiqi) with a thickness of 100 μm.

[0067] The film layer was placed on a mold with a curvature of 88° and the temperature was 240°C. After hot bending, the base film broke. Hot bending failed.

[0068] On the flat film, firstly, a hardening coating liquid (Japanese Shin-Etsu SY-5211) was applied on the triacetyl cellulose film, and then dried in an oven at 80°C for 5 minutes; then, it was cured by ultraviolet light with a UV energy of 400mJ / cm 2 ; A hardened coating is formed with a thickness of 3μm, a hardness of 3H, and an adhesion of 5B. A common protective film (Shenzhen Bo Chuangda ST36065L) is attached. A pressure-sensitive adhesive (Dow-Corning 7657, USA) is applied on the other side of the hardened TAC film and dried and cured. A release film (Dongguan Yuancai F5070) is attached to obtain a finished product.

[0069] Comparative Example 2

[0070] Comparative Example 2 is basically the same as Example 1, except that the base film material used is a non-zero phase difference film, and the base film layer is a commercially available cellulose acetate film (Dongguan Meiqi) with a thickness of 100 μm.

[0071] The film layer was placed on a mold with a curvature of 88° and the temperature was 240℃. After hot bending, the base film was severely deformed. Hot bending failed.

[0072] On the flat film, firstly, the hardening coating liquid (Japanese Shin-Etsu SY-5211) was coated on the cellulose acetate film, and then dried in an oven at 80°C for 5 minutes; then, it was cured by ultraviolet light with UV energy of 400mJ / cm 2 ; A hardened coating is formed with a thickness of 3μm, a hardness of 3H, and an adhesion of 5B. A common protective film (Shenzhen Bo Chuangda ST36065L) is attached. A pressure-sensitive adhesive (US Dow-Corning 7657) is applied on the other side of the hardened CA film and dried and cured. A release film (Dongguan Yuancai F5070) is attached to obtain a finished product.

[0073] Comparative Example 3

[0074] Comparative Example 3 is substantially the same as Example 2, except that the base film layer used is a commercially available transparent thermoplastic polyurethane film (Bayer 786L, Germany) with a thickness of 100 μm.

[0075] First, a hardening coating liquid (Japanese Shin-Etsu SY-5211) was applied on the thermoplastic polyurethane base film and dried in an oven at 80°C for 5 min. Then, the film was cured by ultraviolet light with a UV energy of 400 mJ / cm 2 ; Form a hardened coating with a thickness of 3μm, a hardness of 3H, and an adhesion of 5B. Apply a common protective film (Shenzhen Bo Chuangda ST36065L). Apply a pressure-sensitive adhesive (Dow-Corning 7657, USA) on the other side of the hardened TPU film and dry and solidify. Apply a release film (Dongguan Yuancai F5070). Use a hot press to bend at 200℃ to obtain a finished product.

[0076] Comparative Example 4

[0077] Comparative Example 4: TOYOBO COSMOSHINE The film is used as the base film with a thickness of 100 μm.

[0078] The film layer was placed on a mold with a curvature of 88° and the temperature was 240℃. After hot bending, the base film was severely deformed. Hot bending failed.

[0079] On the flat film, first apply the hardening coating liquid (Japanese Shin-Etsu SY-5211) on the TOYOBO SRF film, dry it in an oven, and set the oven temperature to 80℃ for 5 minutes; then cure it with UV light, and the UV energy is 400mJ / cm 2; A hardened coating is formed with a thickness of 3μm, a hardness of 3H, and an adhesion of 5B. A common protective film (Shenzhen Bo Chuangda ST36065L) is attached. A pressure-sensitive adhesive (Dow-Corning 7657, USA) is applied on the other side of the hardened PET film and dried and cured. A release film (Dongguan Yuancai F5070) is attached to obtain a finished product.

[0080] Comparative Example 5

[0081] Comparative Example 5 uses polycarbonate film (Sichuan Longhua 811) as the base film with a thickness of 100 μm. This material film cannot be hardened. The material is brittle and cannot be hot-bent.

[0082] First, a common protective film (Shenzhen Bo Chuangda ST36065L) was attached to a polycarbonate film (Sichuan Longhua PC 811). A pressure-sensitive adhesive (US Dow-Corning 7657) was applied to the other side of the polycarbonate film, dried and cured. A release film (Dongguan Yuancai F5070) was attached to obtain a finished product.

[0083] Table 2 Performance test results of films prepared in Examples 1 to 6 of the present invention and Comparative Examples 1 to 5

[0084]

[0085]

[0086]

[0087]

[0088] It can be seen from the above embodiments that the present invention provides an under-screen fingerprint optical unlocking screen protective film, including a hardened coating, a cellulose diacetate film layer, a pressure-sensitive adhesive layer and a release film layer that are in contact with each other in sequence. The protective film provided by the present invention uses a transparent cellulose diacetate film layer with zero phase difference as a base film, which is compounded with other layers, so that the protective film has zero phase difference, a light transmittance of >90%, a haze of <3%, and a high response sensitivity to the under-screen optical recognition system; good stiffness, and a tensile strength of >80N / mm 2, will not leave indentations on the optical screen protective film; high hardness, >2H (500g), good wear resistance, >1000 times (#0000 steel wool, 1kg), small surface friction, dynamic friction coefficient <0.1); can be hot-bent, and the molding surface precision is high, fit the large arc curved screen without warping; biodegradable, environmentally friendly. The experimental results show that: the transmittance is 90-92%; the haze is 0.3-0.5; the hardness is 3H; the wear resistance is >1000 times; there is no phase difference; the tensile strength TD / MD is (150-200) / (230-250)MPa; the elongation at break TD / MD is (150-250) / (140-240)%; when the curved film is curved, the flat surface has excellent fit with a curvature of 88°.

[0089] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An under-screen fingerprint optical unlocking screen protective film, comprising a hardened coating layer, a cellulose diacetate film layer, a pressure-sensitive adhesive layer and a release film layer in contact with each other in sequence; The cellulose diacetate film layer has a light transmittance of >90%, a haze of <3%, zero phase difference, and a tensile strength of >80N / mm 2 ; The hardened coating is an acrylic coating with a breaking elongation>150% and a dynamic friction coefficient<0.1; The thickness of the cellulose diacetate film layer is 14 to 500 μm; The thickness of the hardened coating is 1 to 10 μm; The thickness of the pressure-sensitive adhesive layer is 20 to 80 μm.

2. The under-screen fingerprint optical unlocking screen protective film according to claim 1, characterized in that: The surface of the hardened coating layer is attached to a protective film layer.

3. The under-screen fingerprint optical unlocking screen protective film according to claim 1, characterized in that: The peeling force of the pressure-sensitive adhesive layer on the anti-fingerprint coated glass is greater than 15gf / 25mm.

4. The under-screen fingerprint optical unlocking screen protective film according to claim 1, characterized in that: A thermoplastic polyurethane film layer may also be disposed between the cellulose diacetate film layer and the pressure-sensitive adhesive layer.

5. A method for preparing the under-screen fingerprint optical unlocking screen protective film according to any one of claims 1 to 4, comprising the following steps: The hardening coating liquid is applied on the cellulose diacetate film, and then dried and cured by ultraviolet light to obtain a hardening coating-cellulose diacetate film composite layer; A pressure-sensitive adhesive is coated on the surface of the cellulose diacetate film of the hardened coating-cellulose diacetate film composite layer and then a release film is attached or a pressure-sensitive adhesive with a release film is directly attached to obtain an under-screen fingerprint optical unlocking screen protective film.

6. The preparation method according to claim 5, characterized in that: The under-screen fingerprint optical unlocking screen protective film is then hot-bent to obtain a curved under-screen fingerprint optical unlocking screen protective film.

7. A method for preparing the under-screen fingerprint optical unlocking screen protective film according to any one of claims 1 to 4, comprising the following steps: The cellulose diacetate film is heat-bent into shape and then cooled; The hardening coating liquid is applied on the cellulose diacetate film, and then dried and cured by ultraviolet light to obtain a hardening coating-cellulose diacetate film composite layer; A pressure-sensitive adhesive with a release film is attached to the surface of the cellulose diacetate film of the hardened coating-cellulose diacetate film composite layer to obtain a fingerprint optical unlocking screen protective film under the curved screen.

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