A light-shielding adhesive tape for a folding screen metal support and a preparation method and application thereof

Abstract

This application relates to the field of adhesive tape technology, specifically disclosing a light-shielding tape for a foldable screen metal bracket, its preparation method, and its application. The light-shielding tape for the foldable screen metal bracket comprises, from the outside to the inside, a black ink layer, a primer layer, a substrate layer, an adhesive layer, and a protective layer. The black ink layer comprises the following raw materials: waterborne polyurethane, a light-shielding agent, a nonionic polycarboxylate dispersant, a blocked isocyanate crosslinking agent, a polyurethane elastomer toughening agent, polyethylene glycol, antioxidant 1010, and a solvent. The light-shielding agent is obtained by activating and modifying carbon black, grafting it with polyethylene glycol, then treating it with positively charged nano-titanium dioxide through a microfluidic chip dual-channel process, and finally coating it with polyurethane-acrylate. The light-shielding tape prepared in this application exhibits excellent light-shielding performance when used for foldable screen metal brackets.

Description

Technical Field

[0001] This application relates to the field of adhesive tape technology, and more specifically, to a light-shielding adhesive tape for a foldable screen metal bracket, its preparation method, and its application. Background Technology

[0002] As consumer electronics devices rapidly evolve towards thinner, lighter, and more flexible designs, foldable smartphones and tablets have become mainstream market trends. In the core structure of these devices, the metal frame plays a crucial role. It not only provides a stable support frame for the flexible screen, preventing deformation and breakage during repeated folding, but also provides structural protection for internal optical components such as the backlight module, image sensor, and fingerprint recognition module, ensuring the installation accuracy and operational stability of these optical components.

[0003] However, foldable screen devices have stringent requirements for light shielding in terms of optical performance. On the one hand, if light leakage occurs during the operation of the backlight module, it can lead to problems such as whitening and uneven brightness in the screen display area, severely affecting the visual experience. On the other hand, if the gap between the metal bracket and the optical components cannot effectively shield light, external stray light or internal light leakage can interfere with the signal acquisition of the image sensor, resulting in malfunctions such as degraded image quality and reduced fingerprint recognition sensitivity. Therefore, special light-shielding tape must be used at the joints between the metal bracket and the optical components, and at the junctions between the bracket and the screen frame, to achieve the dual functions of structural fixation and light-shielding sealing. For example, patent application CN118580797A discloses a method for preparing a light-shielding tape for a wireless charger. This method includes a black ink layer, a substrate layer, and an adhesive layer. The black ink layer and the adhesive layer are located on the upper and lower surfaces of the substrate layer, respectively. A release layer is provided on the side of the adhesive layer opposite to the substrate layer. The black ink layer is obtained by drying black ink, which is prepared through the following steps: S1, mixing 60-80 parts of waterborne polyurethane, 15-25 parts of deionized water, 1-5 parts of 1,1,1-methylenetris(4-isocyanate)benzene, and 0.1-0.3 parts of trimer... Sodium phosphate is added to a high-speed stirring dispersant and stirred at 300-500 rpm until homogeneous. In step S2, 1-5 parts carbon black, 1-1.5 parts sodium silicate, 1-5 parts polyethyleneimine, 0.5-2 parts octadecyl dimethyl benzyl ammonium chloride, and 0.5-1.5 parts coupling agent are added, and the stirring speed is adjusted to 500-600 rpm until homogeneous. In step S3, 1-1.5 parts carboxymethyl cellulose, 2-4 parts light absorber, and 0.5-1 part chitosan are added, and the stirring speed is increased to 800-1100 rpm. The mixture is stirred for 15-30 minutes to obtain black ink. In step S4, the black ink is coated onto a substrate layer and dried to obtain a black ink layer. While this light-blocking tape is fingerprint-resistant and leaves no fingerprint residue after repeated use in various environments, preventing corrosion from fingerprints and sweat stains, the cationic additives (polyethyleneimine, octadecyl dimethyl benzyl ammonium chloride) and the inorganic electrolyte sodium silicate can cause excessive adsorption with the negative charge on the carbon black surface. Furthermore, the carbon black is only stirred, preventing stable and uniform dispersion in the ink system, resulting in the formation of agglomerates of varying sizes. These agglomerates disrupt the uniform distribution of light-blocking sites. On one hand, the carbon black particles within the agglomerates cannot fully contact light, essentially wasting effective light-blocking components. On the other hand, tiny gaps form between the agglomerates, allowing light to penetrate the ink layer. Additionally, the low addition of only 1-5 parts of carbon black, coupled with uneven dispersion, makes it even more difficult to form a continuous light-blocking network, ultimately reducing the light-blocking effect. Summary of the Invention

[0004] To improve the light-blocking effect of light-blocking tape, this application provides a light-blocking tape for a foldable screen metal bracket, its preparation method, and its application.

[0005] In a first aspect, this application provides a light-shielding tape for a foldable screen metal bracket, employing the following technical solution:

[0006] A light-shielding tape for a foldable screen metal bracket comprises, from the outside to the inside, a black ink layer, a primer layer, a substrate layer, an adhesive layer, and a protective layer.

[0007] The black ink layer comprises the following raw materials in parts by weight: 55-65 parts of waterborne polyurethane, 15-20 parts of opacifier, 1-2 parts of nonionic polycarboxylate dispersant, 3-5 parts of blocked isocyanate crosslinking agent, 5-8 parts of polyurethane elastomer toughening agent, 1-2 parts of polyethylene glycol, 0.3-0.8 parts of antioxidant 1010, and 18-25 parts of solvent;

[0008] The method for preparing the light-blocking agent includes the following steps:

[0009] (1) After activating and modifying 10 parts by weight of carbon black, grafting 2-3 parts by weight of polyethylene glycol yields modified carbon black with a negatively charged surface.

[0010] (2) Disperse 8-10 parts by weight of the modified carbon black and 5-8 parts by weight of nano-titanium dioxide with positive surface charge in 40-50 parts by weight of an aqueous solution with pH=5, and obtain a suspension by mixing through a dual-channel microfluidic chip.

[0011] (3) Add 6-10 parts by weight of polyurethane-acrylate prepolymer and 0.3-0.6 parts by weight of initiator to the suspension for reaction. After the reaction is completed, centrifuge, filter, wash and dry to obtain the light-blocking agent.

[0012] By adopting the above technical solution, the light-shielding agent of this application first modifies carbon black by grafting polyethylene glycol, and then uses microfluidic technology to electrostatically adsorb the modified carbon black and titanium dioxide, so that titanium dioxide is uniformly loaded on the surface of the modified carbon black to form composite particles. Then, combined with organic reaction, the polymer coats the composite particles to form a light-shielding agent. This process not only effectively solves the problem of easy agglomeration of traditional carbon black in ink system, but also achieves uniform dispersion of carbon black and titanium dioxide in ink system. It also makes the two form a synergistic light-shielding network of carbon black light absorption and titanium dioxide light reflection, which improves the light-shielding properties of black ink layer, and thus improves the light-shielding effect of the produced light-shielding tape in the metal frame of folding screen.

[0013] Preferably, in step (1), the specific preparation method of the modified carbon black is as follows: 10 parts by weight of carbon black are treated with oxygen plasma to obtain activated carbon black; the activated carbon black is added to 25-35 parts by weight of deionized water to form a suspension, and then 2-3 parts by weight of polyethylene glycol and 0.06-0.12 parts by weight of catalyst are added. The mixture is stirred and reacted at 60-70°C for 3-4 hours, and then filtered, washed and dried to obtain polyethylene glycol grafted modified carbon black.

[0014] By adopting the above technical solution, oxygen plasma treatment can activate the carbon black surface and introduce oxygen-containing active groups such as hydroxyl and carboxyl groups. These groups provide sufficient reaction sites for the grafting of polyethylene glycol. Combined with a reaction temperature of 60-70℃ and the action of a catalyst, it can promote the chemical bonding between the hydroxyl groups in the polyethylene glycol molecule and the oxygen-containing groups on the carbon black surface, which can significantly improve the grafting efficiency and grafting stability of polyethylene glycol. The grafted polyethylene glycol not only enhances the hydrophilicity of the modified carbon black, but the hydroxyl groups on its molecular chain can also form hydrogen bonds with the hydroxyl groups on the surface of titanium dioxide. At the same time, the oxygen-containing functional groups (negatively charged) remaining on the carbon black surface can generate electrostatic adsorption with the positively charged titanium dioxide. Under the dual action, the interfacial compatibility between the modified carbon black and titanium dioxide is significantly improved, thereby increasing the bonding strength between the two.

[0015] Preferably, the molecular weight of the polyethylene glycol is 2000-6000.

[0016] While low molecular weight polymers improve grafting efficiency due to their high hydroxyl density, their thin grafted layers and low steric hindrance make them prone to particle agglomeration and unable to effectively bridge the gap between carbon black and titanium dioxide, resulting in weak interfacial interaction. High molecular weight polymers, on the other hand, suffer from significant steric hindrance due to their long chain length, reducing the grafting rate and making them prone to molecular entanglement. This affects dispersion uniformity and increases system viscosity, weakening the uniformity of bonding with titanium dioxide. Only medium molecular weight polymers (2000-6000 Da) can balance reactivity and steric hindrance, ensuring efficient grafting and good dispersion. Furthermore, their moderate chain length allows for the formation of stable hydrogen bonds and effective electrostatic adsorption, strengthening the bond with titanium dioxide and thus ensuring the dispersibility and final performance of the opacifier.

[0017] Preferably, the gas source for the oxygen plasma treatment is a mixture of oxygen and argon in a volume ratio of (1-3):(7-9).

[0018] By adopting the above technical solution, oxygen, as an active component, can efficiently introduce oxygen-containing active groups such as hydroxyl and carboxyl groups onto the carbon black surface, providing sufficient reaction sites for the subsequent polyethylene glycol grafting reaction; argon, as an inert component, can effectively dilute the oxygen concentration, stabilize the plasma discharge environment, and prevent the carbon black surface from being damaged by excessive oxidation, thus preventing structural instability. At the same time, it can improve the uniformity of the distribution of active groups through ion bombardment, thereby ensuring the bonding effect between modified carbon black and titanium dioxide and the dispersibility and performance stability of the final opacifier.

[0019] Preferably, in step (3), 6-10 parts by weight of polyurethane-acrylate prepolymer, 3-5 parts by weight of tetraethyl orthosilicate and 0.3-0.6 parts by weight of initiator are added to the suspension for reaction. After the reaction is completed, the mixture is centrifuged, filtered, washed and dried to obtain the light-blocking agent.

[0020] By adopting the above technical solution, tetraethyl orthosilicate hydrolyzes in aqueous solution to generate silanol groups, which then undergo condensation reactions with the hydroxyl groups on the carbon black core and titanium dioxide surface to form a three-dimensional cross-linked SiO2 inorganic network. This network intertwines with the subsequently in-situ polymerized polyurethane-acrylate polymer to construct an inorganic-organic composite shell. This can improve the density and mechanical strength of the shell, preventing the single organic shell from being damaged during ink grinding and tape bending. At the same time, the interfacial bonding force between the shell and the inorganic structure is strengthened through covalent bond anchoring. Furthermore, the excellent chemical stability of SiO2 significantly improves the high and low temperature resistance and damp heat resistance of the composite particles, ensuring the reliability of the foldable screen light-shielding tape for long-term use.

[0021] Preferably, in step (3), the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:(0.15-0.25).

[0022] Preferably, the solvent is a mixture of deionized water and propylene glycol methyl ether in a mass ratio of (2.5-3.5):1;

[0023] Preferably, the protective layer is a PET film with a thickness of 25-50 μm;

[0024] The substrate layer is a BOPET film with a thickness of 12-25 μm;

[0025] The primer layer is a polyurethane primer with a coating amount of 0.5-1.0 g / m². 2 ;

[0026] The adhesive layer is a water-based acrylic pressure-sensitive adhesive, with a coating amount of 10-15 g / m². 2 .

[0027] Secondly, this application provides a method for preparing light-shielding tape for a foldable screen metal bracket, using the following technical solution:

[0028] A method for preparing a light-shielding tape for a foldable screen metal bracket includes the following steps:

[0029] S1. Weigh out waterborne polyurethane, solvent, nonionic polycarboxylate dispersant, polyurethane elastomer toughening agent, polyethylene glycol, and antioxidant according to the formula, mix them evenly, add opacifier and mix, and finally add blocked isocyanate crosslinking agent, stir and degas to obtain black ink.

[0030] S2, a polyurethane primer is applied to one side of the substrate layer and dried to form a primer layer; the black ink is applied to the surface of the primer layer and dried to form a black ink layer; a water-based acrylic pressure-sensitive adhesive is applied to the other side of the substrate layer, dried, and then a protective layer is attached, cured, and cooled to obtain a composite tape.

[0031] By adopting the above technical solutions, the primer layer and adhesive layer improve the interlayer chemical bonding and adhesion reliability, avoiding interlayer delamination; the high light-blocking advantage of the black ink layer complements the supporting toughness of the substrate layer and the protective performance of the protective layer, resulting in high light-blocking rate and stability; the bending resistance of the substrate layer, the composite shell strength of the light-blocking agent, and the environmental resistance of the adhesive and protective layer combine to achieve good bending resistance of the tape; at the same time, the thickness and performance of each layer are matched, taking into account low residue and easy operation, ultimately allowing the overall tape to break through the limitations of single function and achieve a synergistic unity of light-blocking effect and structural stability.

[0032] Thirdly, this application provides an application of light-shielding tape for a foldable screen metal bracket, employing the following technical solution:

[0033] An application of light-shielding tape for a foldable screen metal bracket involves using a pad printing tool to print a black ink border at the camera opening of the foldable screen metal bracket and covering the side of the foldable screen metal bracket (printed on the side wall perpendicular to the thickness direction); simultaneously, the light-shielding tape for the foldable screen metal bracket is attached to the back of the foldable screen metal bracket.

[0034] By adopting the above technical solution, a black ink border is printed on the camera opening of the metal bracket using a pad printing method, covering the side of the bracket. Combined with the composite tape attached to the back, a comprehensive and synergistic light-shielding structure is formed. This structure utilizes the dual light-shielding effect of the ink border and the composite tape, combined with the full-coverage design on the side, to create a continuous light barrier, effectively blocking light leakage and ambient light reflection. It also avoids the micro-steps and surface deformation problems caused by traditional cover plate printing ink, significantly improving the flatness of the camera hole area, preventing Newton's rings and astigmatism, and ensuring the image quality of the camera. At the same time, the properties of the composite tape are suitable for folding scenarios, absorbing vibrations during folding, further enhancing structural stability and reliability, perfectly meeting the light-shielding and flexible use requirements of foldable screen metal brackets.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. The light-blocking agent of this application is prepared by carbon black modification, microfluidic composite titanium dioxide and in-situ sol-gel coating process. It not only solves the problem of easy agglomeration of traditional carbon black in ink, but also achieves uniform dispersion of carbon black and titanium dioxide, and forms a light-absorbing and light-reflecting synergistic light-blocking network, thereby improving the light-blocking properties of black ink and the light-blocking effect of light-blocking tape for folding screen metal bracket.

[0037] 2. This application uses oxygen plasma to activate carbon black, introducing oxygen-containing active groups to provide reaction sites for polyethylene glycol grafting, promoting chemical bonding between the two to improve grafting efficiency and stability; the grafted polyethylene glycol not only enhances the hydrophilicity of carbon black, but also improves the interfacial compatibility between modified carbon black and titanium dioxide through the dual effects of hydrogen bonding and electrostatic adsorption, thereby increasing the bonding strength between the two.

[0038] 3. In the preparation of the light-shielding agent, tetraethyl orthosilicate is introduced. The silanol groups generated by its hydrolysis condense with the carbon black core and the hydroxyl groups on the surface of titanium dioxide to form a three-dimensional cross-linked SiO2 inorganic network, which interweaves with the polyurethane-acrylate polymer to form an inorganic-organic composite shell. This not only improves the density and mechanical strength of the shell, preventing damage during grinding and bending, and strengthening the interfacial bonding force, but also improves the high and low temperature resistance and damp heat resistance of the composite particles by taking advantage of the excellent stability of SiO2, ensuring the reliability of the foldable screen light-shielding tape for long-term use. Detailed Implementation

[0039] The present application will be further described in detail below with reference to the embodiments.

[0040] Unless otherwise specified, the raw materials used in the preparation examples, embodiments, and comparative examples of this application are all commercially available.

[0041] Preparation Example 1

[0042] This preparation example provides a method for preparing a light-blocking agent, specifically including the following steps:

[0043] (1) 10g of carbon black was activated by plasma treatment for 7min at a power of 120W using a mixed gas of oxygen and argon with a volume ratio of 2:8. The activated carbon black was added to 30g of deionized water and stirred to form a uniform suspension. Then, 2.5g of polyethylene glycol with a molecular weight of 4000 and 0.09g of dibutyltin dilaurate (catalyst) were added. The mixture was heated to 65℃ and stirred for 3.5h. After the reaction was completed, the mixture was centrifuged and filtered, washed 3 times with deionized water, and dried under vacuum at 80℃ for 4h to obtain modified carbon black. The potential of the modified carbon black was tested using a Zeta potentiometer and the potential of the modified carbon black was measured to be -24mV.

[0044] (2) 45g of deionized water was adjusted to pH 5 with 1mol / L dilute hydrochloric acid to obtain a solution. 6.5g of anatase nano titanium dioxide with a particle size of 20-50nm was added to the pH-adjusted deionized water and dispersed at 1000r / min for 10min to obtain a solution. The potential of the solution was tested using a Zeta potentiometer and the potential of the solution was measured to be 21mV. 9g of the above modified carbon black was added to the solution and dispersed at 2000r / min for 20min. Then, a suspension was obtained by mixing in two channels for 5min with a channel flow rate ratio of 1:1, a mixing pressure of 0.4MPa, a channel size of 100μm×200μm, and a mixing chamber volume of 50μL.

[0045] (3) Add 8g of polyurethane-acrylate prepolymer (purchased from Shanghai Yinchang New Materials Co., Ltd., model YC2200), 0.38g of ammonium persulfate and 0.07g of sodium bisulfite to the above suspension, heat to 75℃, stir and react for 2.5h. After the reaction is completed, centrifuge and filter, wash twice with deionized water and once with anhydrous ethanol, and vacuum dry at 60℃ for 6h to obtain the light-blocking agent.

[0046] Preparation Example 2

[0047] This preparation example is basically the same as Preparation Example 1, except that in step (3), 8g of polyurethane-acrylate prepolymer (purchased from Shanghai Yinchang New Materials Co., Ltd., model YC2200), 4g of tetraethyl orthosilicate, 0.38g of ammonium persulfate and 0.07g of sodium bisulfite are added to the above suspension, heated to 75°C, stirred and reacted for 2.5h, after the reaction was completed, centrifuged and filtered, washed twice with deionized water and once with anhydrous ethanol, and vacuum dried at 60°C for 6h to obtain the light-blocking agent.

[0048] Preparation Example 3

[0049] This preparation example provides a method for preparing a light-blocking agent, specifically including the following steps:

[0050] (1) 10g of carbon black was activated by plasma treatment for 7min at a power of 120W using a mixed gas of oxygen and argon with a volume ratio of 1:9. The activated carbon black was added to 25g of deionized water and stirred to form a uniform suspension. Then, 2g of polyethylene glycol with a molecular weight of 6000 and 0.06g of dibutyltin dilaurate (catalyst) were added. The mixture was heated to 70℃ and stirred for 3h. After the reaction was completed, the mixture was centrifuged and filtered, washed 3 times with deionized water, and dried under vacuum at 80℃ for 4h to obtain modified carbon black. The potential of the modified carbon black was tested using a Zeta potentiometer and the potential of the modified carbon black was measured to be -21mV.

[0051] (2) 40g of deionized water was adjusted to pH 5 with 1mol / L dilute hydrochloric acid to obtain a solution. 5g of anatase nano titanium dioxide with a particle size of 20-50nm was added to the pH-adjusted deionized water and dispersed at 1000r / min for 10min to obtain a solution. The potential of the solution was tested using a Zeta potentiometer and the potential of the solution was measured to be 22mV. 8g of the above modified carbon black was added to the solution and dispersed at 2000r / min for 20min. Then, a microfluidic chip with a channel flow rate ratio of 1:1, a mixing pressure of 0.4MPa, a channel size of 100μm×200μm, and a mixing chamber volume of 50μL was used for dual-channel mixing for 5min to obtain a suspension.

[0052] (3) Add 6g of polyurethane-acrylate prepolymer (purchased from Shanghai Yinchang New Materials Co., Ltd., model YC2200), 3g of tetraethyl orthosilicate, 0.26g of ammonium persulfate and 0.04g of sodium bisulfite to the above suspension, heat to 75℃, stir and react for 2.5h. After the reaction is completed, centrifuge and filter, wash twice with deionized water and once with anhydrous ethanol, and vacuum dry at 60℃ for 6h to obtain the light-blocking agent.

[0053] Preparation Example 4

[0054] This preparation example provides a method for preparing a light-blocking agent, specifically including the following steps:

[0055] (1) 10g of carbon black was activated by plasma treatment for 7min at a power of 120W using a mixed gas of oxygen and argon with a volume ratio of 3:7. The activated carbon black was added to 35g of deionized water and stirred to form a uniform suspension. Then, 3g of polyethylene glycol with a molecular weight of 2000 and 0.12g of dibutyltin dilaurate (catalyst) were added. The mixture was heated to 60℃ and stirred for 4h. After the reaction was completed, the mixture was centrifuged and filtered, washed 3 times with deionized water, and dried under vacuum at 80℃ for 4h to obtain modified carbon black. The potential of the modified carbon black was tested using a Zeta potentiometer and the potential of the modified carbon black was measured to be -29mV.

[0056] (2) 50g of deionized water was adjusted to pH 5 with 1mol / L dilute hydrochloric acid to obtain a solution. 8g of anatase nano titanium dioxide with a particle size of 20-50nm was added to the pH-adjusted deionized water and dispersed at 1000r / min for 10min to obtain a solution. The potential of the solution was tested using a Zeta potentiometer and the potential of the solution was measured to be 20mV. 10g of the above modified carbon black was added to the solution and dispersed at 2000r / min for 20min. Then, a suspension was obtained by mixing in two channels for 5min with a channel flow rate ratio of 1:1, a mixing pressure of 0.4MPa, a channel size of 100μm×200μm, and a mixing chamber volume of 50μL.

[0057] (3) Add 10g of polyurethane-acrylate prepolymer (purchased from Shanghai Yinchang New Materials Co., Ltd., model YC2200), 5g of tetraethyl orthosilicate, 0.48g of ammonium persulfate and 0.12g of sodium bisulfite to the above suspension, heat to 75℃, stir and react for 2.5h. After the reaction is completed, centrifuge and filter, wash twice with deionized water and once with anhydrous ethanol, and vacuum dry at 60℃ for 6h to obtain the light-blocking agent.

[0058] Example 1

[0059] This embodiment provides a light-shielding tape for a foldable screen metal bracket, which consists of a black ink layer, a primer layer, a substrate layer, an adhesive layer, and a protective layer from the outside to the inside.

[0060] This embodiment also provides a method for preparing the above-mentioned light-shielding tape for the metal bracket of the foldable screen, including the following steps:

[0061] Weigh out 60g of waterborne polyurethane (purchased from Jining Ribuluo Biotechnology Co., Ltd., product number AL-641687592489), 16.5g of deionized water, 5.5g of propylene glycol methyl ether (PGME), and 1.5g of nonionic polycarboxylate dispersant (Arkema Coadis dispersant). ® BR85), 6.5g polyurethane elastomer toughening agent (Wanhua Chemical) ® WHT-1185EC), 1.5g of hydroxyl-terminated polyethylene glycol with a molecular weight of 4000 and 0.6g of antioxidant 1010 were stirred at 500r / min for 15min to obtain a mixture; 17.5g of opacifier was added to the mixture and dispersed at 1500r / min for 30min, and the particle size was controlled to be ≤300nm by grinding; finally, 4g of blocked isocyanate crosslinking agent (blocked isocyanate curing agent DXB-3465D purchased from Shaoguan Dongsen Synthetic Materials Co., Ltd.) was added, and the mixture was stirred at low speed of 300r / min for 10min and degassed for 20min to obtain black ink; the opacifier used was the one obtained in Preparation Example 1;

[0062] A 20μm thick BOPET film was used as the substrate layer, and a polyurethane primer (purchased from Shanghai Senhao Electronics Technology Co., Ltd., item number TEROSONPU8522RF) was coated on one side of it with a coating amount of 0.8g / m. 2 Dry at 100℃ for 30 seconds to form a primer layer; apply the aforementioned black ink to the surface of the primer layer, with a coating amount of 6 g / m². 2 A black ink layer is formed by hot air drying at 120℃ for 60 seconds; a water-based acrylic pressure-sensitive adhesive (VONCOAT W-386) is then coated on the other side of the substrate layer at a coating weight of 12g / m². 2Pre-dry at 80℃ for 40s, then laminate with a 35μm thick PET protective layer, and cure at 105℃ for 2min to obtain a composite. Cool the composite to room temperature and age at 40℃ for 24h to obtain a light-shielding tape.

[0063] In this embodiment, the light-shielding tape is used for the metal bracket of the folding screen. Specifically, the metal bracket is made of stainless steel (SUS) with a thickness of 100μm. It is pre-etched, and the camera and bending areas are hollowed out. A black ink border is printed on the camera opening of the metal bracket using pad printing. The width of the printed circle is 0.5mm (the printing size is 1mm larger than the diameter of the opening of the metal bracket). The pad printing head also prints on the side of the metal bracket (the side wall printing is perpendicular to the thickness direction). The metal bracket needs to be plasma treated before printing. The black tape is formed by die-cutting with a circular knife, removing the protective layer and not pre-drilling holes at the camera hole. After being attached to the metal bracket, the printed circular hole on the metal bracket is grasped by laser equipment for visual recognition and cutting. The size is 0.2mm smaller than the diameter of the bracket opening.

[0064] Example 2

[0065] This embodiment provides a light-shielding tape for a foldable screen metal bracket, which consists of a black ink layer, a primer layer, a substrate layer, an adhesive layer, and a protective layer from the outside to the inside.

[0066] This embodiment also provides a method for preparing the above-mentioned light-shielding tape for the metal bracket of the foldable screen, including the following steps:

[0067] Weigh out 55g of waterborne polyurethane (purchased from Jining Ribuluo Biotechnology Co., Ltd., product number AL-641687592489), 12.9g of deionized water, 5.1g of propylene glycol methyl ether (PGME), and 1g of nonionic polycarboxylate dispersant (Arkema Coadis dispersant). ® BR85), 5g polyurethane elastomer toughening agent (Wanhua Chemical) ® WHT-1185EC), 1g of polyethylene glycol with a molecular weight of 4000 and 0.3g of antioxidant 1010 were stirred at 500r / min for 15min to obtain a mixture; 15g of opacifier was added to the mixture and dispersed at 1500r / min for 30min, and the particle size was controlled to be ≤300nm by grinding; finally, 3g of blocked isocyanate crosslinking agent (blocked isocyanate curing agent DXB-3465D purchased from Shaoguan Dongsen Synthetic Materials Co., Ltd.) was added, and the mixture was stirred at low speed of 300r / min for 10min and degassed for 20min to obtain black ink; the opacifier used was obtained from Preparation Example 1;

[0068] A 12μm thick BOPET film was used as the substrate layer, and a polyurethane primer (purchased from Shanghai Senhao Electronics Technology Co., Ltd., item number TEROSONPU8522RF) was coated on one side of it at a coating weight of 0.5g / m. 2 Dry at 100℃ for 30 seconds to form a primer layer; apply the aforementioned black ink to the surface of the primer layer, with a coating amount of 6 g / m². 2 A black ink layer is formed by hot air drying at 120℃ for 60 seconds; a water-based acrylic pressure-sensitive adhesive (VONCOAT W-386) is then coated on the other side of the substrate layer at a coating weight of 10 g / m². 2 Pre-dry at 80℃ for 40s, then laminate with a 25μm thick PET protective layer, and cure at 105℃ for 2min to obtain a composite. Cool the composite to room temperature and age at 40℃ for 24h to obtain a light-shielding tape.

[0069] In this embodiment, the light-shielding tape is used for the metal bracket of the folding screen. Specifically, the metal bracket is made of titanium (Ti) material with a thickness of 100μm. It is pre-etched and processed, and the camera and bending areas are hollowed out. A black ink border is printed on the camera opening of the metal bracket using pad printing. The width of the printed circle is 0.5mm (the printing size is 1mm larger than the diameter of the opening of the metal bracket). The pad printing head also prints on the side of the metal bracket (the side wall printing is perpendicular to the thickness direction). The metal bracket needs to be plasma treated before printing. The black tape is formed by die-cutting with a circular knife, removing the protective layer and not pre-drilling holes at the camera hole. After being attached to the metal bracket, the printed circular hole on the metal bracket is grasped by laser equipment for visual recognition and cut. The size is 0.2mm smaller than the diameter of the bracket opening.

[0070] Example 3

[0071] This embodiment provides a light-shielding tape for a foldable screen metal bracket, which consists of a black ink layer, a primer layer, a substrate layer, an adhesive layer, and a protective layer from the outside to the inside.

[0072] This embodiment also provides a method for preparing the above-mentioned light-shielding tape for the metal bracket of the foldable screen, including the following steps:

[0073] Weigh out 65g of waterborne polyurethane (purchased from Jining Ribuluo Biotechnology Co., Ltd., product number AL-641687592489), 19.4g of deionized water, 5.6g of propylene glycol methyl ether (PGME), and 2g of nonionic polycarboxylate dispersant (Arkema Coadis dispersant). ® BR85), 8g polyurethane elastomer toughening agent (Wanhua Chemical) ®WHT-1185EC), 2g of polyethylene glycol with a molecular weight of 4000 and 0.8g of antioxidant 1010 were stirred at 500r / min for 15min to obtain a mixture; 20g of opacifier was added to the mixture and dispersed at 1500r / min for 30min, and the particle size was controlled to be ≤300nm by grinding; finally, 5g of blocked isocyanate crosslinking agent (blocked isocyanate curing agent DXB-3465D purchased from Shaoguan Dongsen Synthetic Materials Co., Ltd.) was added, and the mixture was stirred at low speed of 300r / min for 10min and degassed for 20min to obtain black ink; the opacifier used was the one obtained in Preparation Example 1;

[0074] A 25μm thick BOPET film was used as the substrate layer, and a polyurethane primer (purchased from Shanghai Senhao Electronics Technology Co., Ltd., item number TEROSONPU8522RF) was coated on one side at a coating weight of 1.0 g / m². 2 Dry at 100℃ for 30 seconds to form a primer layer; apply the aforementioned black ink to the surface of the primer layer, with a coating amount of 6 g / m². 2 A black ink layer is formed by hot air drying at 120℃ for 60 seconds; a water-based acrylic pressure-sensitive adhesive (VONCOAT W-386) is then coated on the other side of the substrate layer at a coating weight of 15 g / m². 2 Pre-dry at 80℃ for 40s, then laminate with a 50μm thick PET protective layer, and cure at 105℃ for 2min to obtain a composite. Cool the composite to room temperature and age at 40℃ for 24h to obtain a light-shielding tape.

[0075] In this embodiment, the light-shielding tape is used for the metal bracket of the folding screen. Specifically, the metal bracket is made of stainless steel (SUS) with a thickness of 100μm. It is pre-etched, and the camera and bending areas are hollowed out. A black ink border is printed on the camera opening of the metal bracket using pad printing. The width of the printed circle is 0.5mm (the printing size is 1mm larger than the diameter of the opening of the metal bracket). The pad printing head also prints on the side of the metal bracket (the side wall printing is perpendicular to the thickness direction). The metal bracket needs to be plasma treated before printing. The black tape is formed by die-cutting with a circular knife, removing the protective layer and not pre-drilling holes at the camera hole. After being attached to the metal bracket, the printed circular hole on the metal bracket is grasped by laser equipment for visual recognition and cutting. The size is 0.2mm smaller than the diameter of the bracket opening.

[0076] Example 4

[0077] This embodiment is basically the same as Example 1, except that the light-blocking agent used is the one obtained in Preparation 2.

[0078] Example 5

[0079] This embodiment is basically the same as Example 1, except that the light-blocking agent used is the one obtained in Preparation 3.

[0080] Example 6

[0081] This embodiment is basically the same as Example 1, except that the light-blocking agent used is the one obtained in Preparation 4.

[0082] Comparative Example 1

[0083] This comparative example is basically the same as Example 1, except that carbon black is used as the opacifier.

[0084] Performance testing

[0085] Testing standards:

[0086] Dispersion stability: The D50 of the black inks prepared in Examples 1-6 and Comparative Example 1 was tested using a laser particle size analyzer. After standing for 72 hours, the results were observed to see if there was any layering or precipitation. The test results are recorded in Table 1.

[0087] Opacity: The shading tapes prepared in Examples 1-6 and Comparative Example 1 were tested according to GB / T2410-2016, and the test results are recorded in Table 1.

[0088] Bending resistance: The light-shielding tapes prepared in Examples 1-6 and Comparative Example 1 were bonded to stainless steel and tested according to GB / T 33398-2016. The test conditions were: repeated bending at 180° (bending radius 1mm, speed 10 times / min, 100,000 cycles). The test results are recorded in Table 1.

[0089] 180° peel strength: The folding screen metal brackets with light-shielding tape prepared in Examples 1-6 and Comparative Example 1 were tested according to GB / T2792-2014. The test conditions were: 25°C and peel rate of 300 mm / min. The test results are recorded in Table 1.

[0090] Table 1. Performance test data of the light-shielding tape used for the metal bracket of the folding screen in Examples 1-6 and Comparative Example 1.

[0091]

[0092] Referring to Table 1, and combining Example 1 and Comparative Example 1, it can be seen that Example 1, which uses the modified opaque agent of this application (prepared by plasma-activated carbon black grafted with polyethylene glycol, microfluidic composite nano-titanium dioxide, and in-situ sol-gel coating), is significantly superior to Comparative Example 1, which uses pure carbon black as the opaque agent, in terms of core performance: Regarding dispersion stability, the opaque agent particle size D50 of the black ink in Example 1 is only 0.22 μm, and no stratification occurs after standing for 72 hours, while the pure carbon black in Comparative Example 1 has a particle size of 1.85 μm and shows obvious precipitation, proving that the opaque agent modification and composite process of this application effectively solves the problem of easy agglomeration of traditional carbon black; Regarding opacity, the opacity of the opaque tape in Example 1 reaches 99.6%, far exceeding the 95.2% of Comparative Example 1. This demonstrates the advantages of the light-absorbing and light-reflecting synergistic shading network formed by modified carbon black and titanium dioxide. Regarding bending resistance, Example 1 showed no cracks after 100,000 repeated 180° bends (bending radius 1mm), with a light-blocking retention rate of 99.2%, meeting the requirements of foldable screens. In contrast, Comparative Example 1 showed cracking and a light-blocking rate reduced to 88.3%, highlighting the improved structural stability resulting from the adaptive design of the composite shell and tape layers in this application. In terms of 180° peel strength, Example 1's 1.8 N / mm was higher than Comparative Example 1's 1.3 N / mm, indicating that the adhesion reliability between the tape and the metal support in this application is superior. These findings comprehensively demonstrate that the technical solution of this application has achieved significant improvements in light-blocking effect, dispersion stability, bending resistance, and adhesion performance.

[0093] Referring to Table 1 and combining Examples 1 and 4, it can be seen that Example 4, which uses an opaque agent containing tetraethyl orthosilicate (Preparation Example 2), has advantages over Example 1, which uses an opaque agent without tetraethyl orthosilicate (Preparation Example 1), in various performance aspects: Regarding dispersion stability, the particle size D50 of the opaque agent in the black ink of Example 4 is 0.20 μm, slightly smaller than 0.22 μm in Example 1, and no stratification occurred after standing for 72 hours, indicating that the SiO2 inorganic network formed by the hydrolysis of tetraethyl orthosilicate further optimizes the dispersion uniformity of the opaque agent in the ink system; Regarding opacity, the opacity of Example 4 reaches 99.8%, higher than 99.6% in Example 1, demonstrating the effect of the inorganic-organic composite shell on light absorption and reflection. The synergistic effect of the light-shielding network is enhanced. In terms of bending resistance, Example 4 showed no cracks after 100,000 repeated 180° bends, with a light-shielding retention rate of 99.5%, which is better than 99.2% in Example 1. This proves that the three-dimensional cross-linked SiO2 network introduced by tetraethyl orthosilicate improves the mechanical strength and density of the light-shielding agent shell layer and enhances the bending resistance of the tape. In terms of 180° peel strength, the 1.9 N / mm of Example 4 is slightly higher than the 1.8 N / mm of Example 1, indicating that the interfacial bonding force between the composite shell layer and each layer of the tape is better. In summary, the introduction of tetraethyl orthosilicate in the preparation of the light-shielding agent can further improve the dispersion stability, light-shielding effect, bending resistance and bonding reliability of the light-shielding tape.

[0094] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A light-shielding tape for a foldable screen metal bracket, characterized in that, From the outside in, it includes a black ink layer, a primer layer, a substrate layer, an adhesive layer, and a protective layer. The black ink layer comprises the following raw materials in parts by weight: 55-65 parts of waterborne polyurethane, 15-20 parts of opacifier, 1-2 parts of nonionic polycarboxylate dispersant, 3-5 parts of blocked isocyanate crosslinking agent, 5-8 parts of polyurethane elastomer toughening agent, 1-2 parts of polyethylene glycol, 0.3-0.8 parts of antioxidant 1010, and 18-25 parts of solvent; The method for preparing the light-blocking agent includes the following steps: (1) Activated carbon black is obtained by oxygen plasma treatment of 10 parts by weight; the activated carbon black is added to 25-35 parts by weight of deionized water to form a suspension, and then 2-3 parts by weight of polyethylene glycol and 0.06-0.12 parts by weight of catalyst are added. The mixture is stirred at 60-70℃ for 3-4 hours, filtered, washed and dried to obtain modified carbon black. (2) Disperse 8-10 parts by weight of the modified carbon black and 5-8 parts by weight of nano-titanium dioxide with positive surface charge in 40-50 parts by weight of an aqueous solution with pH=5, and obtain a suspension by mixing through a microfluidic chip dual channel; (3) Add 6-10 parts by weight of polyurethane-acrylate prepolymer and 0.3-0.6 parts by weight of initiator to the suspension for reaction. After the reaction is completed, centrifuge, filter, wash and dry to obtain the light-blocking agent.

2. The light-shielding tape for the folding screen metal bracket according to claim 1, characterized in that, The molecular weight of the polyethylene glycol is 2000-6000.

3. The light-shielding tape for the folding screen metal bracket according to claim 1, characterized in that, The gas source for the oxygen plasma treatment is a mixture of oxygen and argon in a volume ratio of (1-3):(7-9).

4. The light-shielding tape for the folding screen metal bracket according to claim 1, characterized in that, Step (3) Add 6-10 parts by weight of polyurethane-acrylate prepolymer, 3-5 parts by weight of tetraethyl orthosilicate and 0.3-0.6 parts by weight of initiator to the suspension for reaction. After the reaction is completed, centrifuge, filter, wash and dry to obtain the light-blocking agent.

5. The light-shielding tape for a folding screen metal bracket according to claim 1, characterized in that, In step (3), the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:(0.15-0.25).

6. The light-shielding tape for the folding screen metal bracket according to claim 1, characterized in that, The solvent is a mixture of deionized water and propylene glycol methyl ether in a mass ratio of (2.5-3.5):

1.

7. The light-shielding tape for a folding screen metal bracket according to claim 1, characterized in that, The protective layer is a PET film with a thickness of 25-50 μm; The substrate layer is a BOPET film with a thickness of 12-25 μm; The primer layer is a polyurethane primer with a coating amount of 0.5-1.0 g / m². 2 ; The adhesive layer is a water-based acrylic pressure-sensitive adhesive, with a coating amount of 10-15 g / m². 2 .

8. A method for preparing a light-shielding tape for a foldable screen metal bracket as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Weigh out waterborne polyurethane, solvent, nonionic polycarboxylate dispersant, polyurethane elastomer toughening agent, polyethylene glycol, and antioxidant according to the formula, mix them evenly, add opacifier and mix, and finally add blocked isocyanate crosslinking agent, stir and degas to obtain black ink. S2, a polyurethane primer is applied to one side of the substrate layer and dried to form a primer layer; the black ink is applied to the surface of the primer layer and dried to form a black ink layer; a water-based acrylic pressure-sensitive adhesive is applied to the other side of the substrate layer, dried, and then a protective layer is attached, cured, and cooled to obtain a composite tape.

9. An application of the light-shielding tape for a folding screen metal bracket as described in any one of claims 1-7, characterized in that, Use a pad printing tool to print a black ink border around the camera opening on the metal bracket of the foldable screen, and also cover the sides of the metal bracket of the foldable screen. Meanwhile, light-shielding tape is attached to the back of the foldable screen metal bracket.

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