Self-repairing coating of touch screen and preparation method of self-repairing coating

Abstract

The invention provides a self-repairing coating of a touch screen and a preparation method of the self-repairing coating, the self-repairing coating is formed by curing sol formed by konjac glucomannan and POSS (Polyhedral Oligomeric Silsesquioxane) modified nano silicon dioxide, and the content of the POSS modified nano silicon dioxide is gradually reduced from the surface of the self-repairing coating to the inside. The self-repairing coating is of a multi-layer stacked structure formed by sequentially coating the surface of the touch screen with sol containing POSS modified nano silicon dioxide with different concentrations and curing the sol. The content of POSS modified nano silicon dioxide on the surface layer of the self-repairing coating is relatively high, more active sites such as amino groups and hydroxyl groups can be provided to serve as anchoring points of dynamic hydrogen bonds or dynamic chemical bonds, the repairing strength of a damaged interface is improved, and the repairing efficiency is improved.

Description

Technical Field

[0001] This application belongs to the technical field of touchscreens, and more particularly, relates to a self-healing coating for touchscreens and a preparation method thereof. Background Art

[0002] The use of electronic touchscreen products is currently very popular. During daily use, touchscreens are easily scratched by sharp objects, resulting in scratches of varying depths, which affect the aesthetics and user experience. Generally, when a scratch on a touchscreen occurs, it gradually spreads from the surface layer of the touchscreen to the inner layer. Therefore, the scratches on the surface layer are usually wider and more severely damaged; as the scratches gradually spread to the inner layer, the scratches are dispersed by stress to form finer and less severe cracks.

[0003] Currently, there are already self-healing coatings for touchscreens that can repair the generated scratches under a certain mechanism, thereby extending the service life of the touchscreens. However, the repair effect on scratches is not very ideal. After the touchscreen is self-healed, the previously scratched marks can still be seen at the original scratch positions, but the scratched marks are significantly faded. It can be seen that there is still room for improvement in the repair strength of the existing self-healing coatings for scratches. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a self-healing coating for touchscreens and a preparation method thereof, so as to solve the technical problem of insufficient scratch repair strength of touchscreens existing in the prior art.

[0005] To achieve the above purpose, the technical solution adopted in this application is: to provide a self-healing coating for touchscreens, which is formed by curing a sol formed by konjac glucomannan and POSS-modified nano-silica, wherein the content of the POSS-modified nano-silica decreases from the surface to the inside of the self-healing coating; the self-healing coating is a multi-layer stacked structure formed by sequentially coating sols containing different concentrations of the POSS-modified nano-silica on the surface of the touchscreen and curing them.

[0006] In one embodiment, the self-healing coating is formed by curing three sols, and a graphene layer with a thickness of 10 - 15 nanometers is coated between every two adjacent cured sols; in the order from the surface to the inside of the self-healing coating, the concentrations of the POSS-modified nano-silica contained in the three sols before curing are 6 g / L, 4 g / L, and 2 g / L respectively, and the thicknesses of the three sols after curing are 50 microns, 30 microns, and 20 microns respectively.

[0007] In one embodiment, the self-healing coating further includes PAMAM-modified nano-silica, and the content of the PAMAM-modified nano-silica decreases from the surface to the inside of the self-healing coating.

[0008] According to another aspect of the present invention, the present invention further provides a method for preparing a self-repairing coating of a touch screen, comprising: Add an appropriate amount of konjac glucomannan powder into deionized water and stir evenly, then divide the formed konjac glucomannan solution into multiple portions; Grafting POSS onto the surface of nano-silica to obtain POSS-modified nano-silica; Sequentially adding different contents of POSS-modified nano-silica to the prepared multiple konjac glucomannan solutions, thereby obtaining multiple mixed sols with successively increasing concentrations of POSS-modified nano-silica; The plurality of mixed sols are sequentially coated on the surface of the same touch screen in the order of increasing concentration of POSS-modified nano-silicon dioxide and preliminarily cured to form a multi-layer stacked structure; The mixed sol is cured through drying and UV curing process to form a self-healing coating.

[0009] In one embodiment, POSS is grafted onto the surface of nano-silica to prepare POSS-modified nano-silica, comprising: Adding nano-silicon dioxide powder into deionized water and performing ultrasonic cleaning to remove impurities and bubbles on the surface of the nano-silicon dioxide; Adding nano-silicon dioxide into tetrafluoroethylene solvent and stirring evenly to form a silicon dioxide dispersion; Dissolving the silane coupling agent in tetrafluoroethylene solvent to form a uniform silane coupling agent solution; The POSS monomer was dissolved in tetrafluoroethylene solvent and added into the silica dispersion simultaneously with the silane coupling agent solution. The mixture was stirred at 70° C. for 4-6 hours and then dried.

[0010] In one embodiment, when POSS is grafted onto the surface of nano-silica to prepare POSS-modified nano-silica, the mass ratio of the nano-silica to POSS is 1.2:1.

[0011] In one embodiment, the konjac glucomannan solution is divided into three portions, and POSS-modified nano-silica is added to the three portions of konjac glucomannan solution in sequence, so that the concentrations of POSS-modified nano-silica in the three portions of mixed sol are 2 g / L, 4 g / L, and 6 g / L, respectively; The method comprises coating the plurality of mixed sols on the surface of the touch screen in the order of increasing concentration of POSS-modified nano-silicon dioxide, including: First, a layer of sol containing POSS-modified nano-silica with a concentration of 2 g / L is coated on the touch screen, and then a layer of graphene is coated after preliminary curing; Next, a sol with a concentration of 4 g / L containing POSS-modified nano-silica is coated on the touch screen. After preliminary curing, a graphene layer is coated again. Then, a sol with a concentration of 6 g / L containing POSS-modified nano-silica is coated on the touch screen. After preliminary curing, a graphene layer is coated again. Finally, through drying and UV curing processes, the three-layer mixed sol is cured to form a self-healing coating. In the order from the surface to the inside of the self-healing coating, the thicknesses of the three-layer mixed sol after curing are 50 microns, 30 microns, and 20 microns in sequence, and the thickness of the graphene layer is 10 - 15 nanometers.

[0012] In one embodiment, the graphene layer is formed by coating through the following steps: Graphene is dispersed in deionized water, and sodium dodecyl sulfate is added as a surfactant. After forming a dispersion through ultrasonic treatment, a film layer with a thickness of 10 - 15 nanometers is sprayed.

[0013] In one embodiment, the following steps are further included: PAMAM is grafted onto the surface of nano-silica to obtain PAMAM-modified nano-silica. Different amounts of PAMAM-modified nano-silica are added to multiple prepared konjac glucomannan solutions in sequence, so that in each konjac glucomannan solution, the mass ratio of POSS-modified nano-silica to PAMAM-modified nano-silica is 1:1.

[0014] In one embodiment, the following step is further included: adding silver nanowires to the konjac glucomannan solution.

[0015] The beneficial effects of the self-healing coating of the touch screen provided by this application are as follows: Compared with the prior art, the self-healing coating of the touch screen provided by this application is formed by curing a sol formed by konjac glucomannan and POSS-modified nano-silica, and the content of the POSS-modified nano-silica decreases from the surface to the inside of the self-healing coating. In this way, the content of the POSS-modified nano-silica on the surface layer of the self-healing coating is relatively high, which can provide more active sites such as amino groups and hydroxyl groups, serving as "anchoring points" for dynamic hydrogen bonds or dynamic chemical bonds, improving the repair strength of the damaged interface and enhancing the repair efficiency. In addition, the high-concentration POSS-modified nano-silica can also increase the mechanical properties and wear resistance of the surface layer of the self-healing coating. The cracks in the inner layer are relatively slight, so the concentration of POSS-modified nano-silica can be relatively low and the concentration of konjac glucomannan can be relatively high, so as to maintain a relatively high light transmittance and toughness, inhibit the cracks from continuing to expand to deeper positions, thereby enhancing the repair strength of the scratches on the touch screen and greatly improving the problem that obvious traces still exist after the scratches in the prior art are repaired. Brief Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a schematic flow chart of the preparation method of the self-healing coating for the touch screen provided by the embodiment of the present application. Detailed Embodiments

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the following further details the present application in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0019] Now, the self-healing coating for the touch screen provided by the embodiment of the present application will be described. The self-healing coating for the touch screen is an ultra-thin coating formed by coating and curing on the surface of a traditional touch screen. It can undergo a chemical reaction when scratched, thereby self-healing the scratch and extending the service life of the touch screen. Specifically, the self-healing coating for the touch screen is formed by curing a sol formed by konjac glucomannan and POSS-modified nano-silica, and the content of POSS-modified nano-silica decreases from the surface to the inside of the self-healing coating.

[0020] Konjac glucomannan, also known as KGM, is a natural high-molecular soluble dietary fiber. It is a high-molecular heteropolysaccharide formed by polymerizing glucose and mannose residues with a molecular ratio of 1:(1.6 - 1.7) through β-1,4 glycosidic bonds to form the main chain, and containing β-1,3 branches and acetyl groups. Konjac glucomannan is a water-soluble non-ionic polysaccharide and has various unique physical and chemical properties such as water solubility, water retention and thickening, stability, suspension, gelation, adhesion, and film formation.

[0021] POSS (polyhedral oligomeric silsesquioxane) is an organic-inorganic hybrid molecule with a special structure. Its molecular size is 1-3 nanometers. Its inner part is a cage-shaped inner shell composed of an alternating inorganic skeleton of Si-O-Si, and the outer layer is surrounded by an organic group, such as an amino group, an aldehyde group, etc. The organic groups outside POSS can react with various groups, so it is often used as a modifier to improve the properties of polymer materials. And POSS-modified silica has a silica as the rigid core, and POSS molecules are grafted on the surface to form an organic-inorganic hybrid interface. Specifically, the surface of nano-silica is rich in hydroxyl groups (-OH), about 4-8 hydroxyl groups per square nanometer; the surface of the cage-shaped silicon-oxygen skeleton (Si-O-Si) of POSS molecules can be modified with organic functional groups (such as hydroxyl groups, amino groups or epoxy groups), and the vertex positions of the cage-shaped three-dimensional structure (such as T8 type) of POSS molecules contain reactive silicon hydroxyl groups (Si-OH). The silicon hydroxyl groups (Si-OH) of POSS are combined with the hydroxyl groups (-OH) on the surface of nano-silica through hydrogen bonds, which can reduce the aggregation of nano-silica; on the other hand, the silicon-oxygen groups of POSS (such as Si-O-R) hydrolyze to form silanols (Si-OH) in an aqueous environment, which can undergo a condensation reaction with the hydroxyl groups on the surface of nano-silica to directly form Si-O-Si covalent bonds; in addition, POSS has a cage-shaped polyhedral structure (such as T8, T10, T12), and its silicon-oxygen skeleton (Si-O-Si) can also be bonded to the hydroxyl groups (-OH) on the surface of nano-silica through a silane coupling reaction, thus forming a three-dimensional network. The amino groups or aldehyde groups, etc. on the surface of nano-silica grafted with konjac glucomannan and POSS are combined through dynamic covalent bonds to form a reversible cross-linked network; when the temperature is higher than 40 °C, the molecular chain movement ability is enhanced, promoting dynamic reorganization, enabling the molecular chains that were broken at the scratched area before to move and reorganize. The exposed organic groups of POSS react with the hydroxyl groups of the surrounding free konjac glucomannan to form new cross-linking points, realizing the self-healing function. Second, the hydroxyl groups of konjac glucomannan form multiple hydrogen bonds with the hydroxyl groups on the surface of nano-silica and the organic side chains of POSS (such as amino groups). When the coating is damaged, the hydrogen bonds are broken, but under temperature stimulation, such as heating to 40 °C, the molecular chain movement ability of konjac glucomannan is enhanced, and the broken hydrogen bonds are dynamically reorganized through the reorientation of hydroxyl groups with hydroxyl groups / amino groups. The functional groups such as amino groups on the surface of nano-silica grafted with POSS can serve as hydrogen bond anchoring points to promote the formation of new hydrogen bonds at the damaged interface, realizing the self-healing of the coating, and the high specific surface area of nano-silica provides more hydrogen bond binding sites, accelerating the repair efficiency.

[0022] In particular, the content of the POSS-modified nano-silica decreases from the surface of the self-healing coating towards the inside. For example, the self-healing coating of the touch screen can be specifically divided into three layers. The surface layer of the self-healing coating is formed by curing a mixed sol with a concentration of POSS-modified nano-silica of 6 g / L; the middle layer of the self-healing coating is formed by curing a mixed sol with a concentration of POSS-modified nano-silica of 4 g / L; and the innermost layer of the self-healing coating is formed by curing a mixed sol with a concentration of POSS-modified nano-silica of 2 g / L. In this way, the content of the POSS-modified nano-silica decreases from the surface of the self-healing coating towards the inside. As we know, when the sliding marks on the touch screen are generated, they gradually spread from the surface layer of the touch screen towards the inner layer. Therefore, the scratches on the surface layer are usually wider and more severely damaged; as the scratches gradually spread towards the inner layer, the scratches are dispersed by stress to form finer and less severe cracks. If all components are uniformly distributed in the thickness direction of the entire self-healing coating, then when encountering relatively severe scratches, it may occur that the self-healing coating has insufficient repair strength for repairing relatively severe scratches on the surface layer, while the self-healing coating is relatively easy to repair relatively fine cracks in the deep layer. Therefore, we specifically decrease the content of the POSS-modified nano-silica in the self-healing coating from the surface of the self-healing coating towards the inside. In this way, the concentration of the POSS-modified nano-silica on the surface layer of the self-healing coating is relatively high, which can provide more active sites such as amino groups and hydroxyl groups, serving as the "anchoring points" of dynamic hydrogen bonds or dynamic chemical bonds, improving the repair strength of the damaged interface and enhancing the repair efficiency. In addition, the high concentration of the POSS-modified nano-silica can also increase the mechanical properties and wear resistance of the surface layer of the self-healing coating. The cracks in the inner layer are relatively slight, so the concentration of the POSS-modified nano-silica can be relatively low, and the concentration of konjac glucomannan can be relatively high, so as to maintain relatively high light transmittance, toughness and adhesion, and inhibit the cracks from continuing to expand to deeper positions.

[0023] The present invention forms a self-healing coating by curing a sol formed by konjac glucomannan and POSS-modified nano-silica, and the content of the POSS-modified nano-silica decreases from the surface of the self-healing coating towards the inside. In this way, the content of the POSS-modified nano-silica on the surface layer of the self-healing coating is relatively high, which can provide more active sites such as amino groups and hydroxyl groups, serving as the "anchoring points" of dynamic hydrogen bonds or dynamic chemical bonds, improving the repair strength of the damaged interface and enhancing the repair efficiency. In addition, the high concentration of the POSS-modified nano-silica can also increase the mechanical properties and wear resistance of the surface layer of the self-healing coating. The cracks in the inner layer are relatively slight, so the concentration of the POSS-modified nano-silica can be relatively low, and the concentration of konjac glucomannan can be relatively high, so as to maintain relatively high light transmittance and toughness, inhibit the cracks from continuing to expand to deeper positions, thereby enhancing the repair strength of the scratches on the touch screen and greatly improving the problem that obvious traces still exist after repairing relatively severe scratches in the prior art.

[0024] In one embodiment, the self-healing coating is a multi-layer stacked structure formed by successively coating sols containing the POSS-modified nano-silica with different concentrations on the surface of the touch screen and curing them. In the actual manufacturing process, multiple portions of sols containing konjac glucomannan and POSS-modified nano-silica are pre-prepared, and the difference between each portion of the sol lies in the different concentrations of the POSS-modified nano-silica. Then, in the order of increasing concentration of the POSS-modified nano-silica, the sols are successively coated on the surface of the touch screen, so as to obtain a self-healing coating in which the content of the POSS-modified nano-silica gradually decreases from the surface to the inside. By adopting this structure and the corresponding batch-by-batch coating method, the operation is simple and the manufacturing cost is relatively lower.

[0025] In one embodiment, the self-healing coating is formed by curing three layers of sols, and a graphene layer with a thickness of 10 - 15 nanometers is coated between every two adjacent cured sols; in the order from the surface to the inside of the self-healing coating, the concentrations of the POSS-modified nano-silica contained in the three layers of sols before curing are 6 g / L, 4 g / L, and 2 g / L respectively, and the thicknesses of the three layers of sols after curing are 50 microns, 30 microns, and 20 microns respectively.

[0026] In the actual operation process, three portions of sols are pre-prepared, and the concentrations of the POSS-modified nano-silica in the three portions of sols are 2 g / L, 4 g / L, and 6 g / L respectively. First, a sol containing the POSS-modified nano-silica with a concentration of 2 g / L is coated on the touch screen, and after preliminary curing, a graphene layer is coated; then, a sol containing the POSS-modified nano-silica with a concentration of 4 g / L is coated on the touch screen, and after preliminary curing, a graphene layer is coated; then, a sol containing the POSS-modified nano-silica with a concentration of 6 g / L is coated on the touch screen, and after preliminary curing, a graphene layer is coated; finally, the three layers of mixed sols can be cured to form a self-healing coating through a drying and UV curing process. In this way, in the order from the surface to the inside of the self-healing coating, the thicknesses of the three layers of mixed sols after curing are 50 microns, 30 microns, and 20 microns in sequence; the thickness of the graphene layer is 10 - 15 nanometers.

[0027] By coating a graphene layer between two adjacent layers of cured sol, as a two-dimensional material, graphene can form a continuous film through solution spraying, thereby combining with the sol cured layer. The graphene layer can provide electrical conductivity and mechanical support, improving the sensitivity and durability of the touch screen. Moreover, the hardness of the graphene layer is greater than that of the cured sol. Therefore, such a self-healing coating forms a "soft-hard-soft" alternating structure. The graphene layer can inhibit crack propagation during sliding of the self-healing coating, reducing interlayer stress concentration. In particular, the layered structure of graphene can inhibit the longitudinal propagation of cracks deeper, thus extending the service life.

[0028] In particular, the thickness of the graphene layer is 10 - 15 nanometers. When the thickness of the graphene layer exceeds 20 nanometers, the light transmittance significantly decreases (<85%), which may affect the screen display effect. While a 10 - 15 nanometer graphene layer can not only meet the requirements of the touch screen for electrical conductivity, but also improve the fracture toughness, maintain a good mechanical strengthening effect, and effectively prevent crack propagation across layers through the two-dimensional sheet structure.

[0029] Furthermore, in the order from the surface to the inside of the self-healing coating, the thicknesses of the three layers of cured sol are 50 microns, 30 microns, and 20 microns respectively. In this way, the outermost layer not only has the highest content of POSS-modified nano-silica but also the thickest thickness; while the innermost layer has the lowest content of POSS-modified nano-silica and the thinnest thickness, thus further optimizing the gradient change of the content of POSS-modified nano-silica in the self-healing coating, making POSS-modified nano-silica distributed as much as possible in the outer layer of the self-healing coating, increasing the repair ability and effect of the surface layer of the self-healing coating.

[0030] In one embodiment, the self-healing coating further includes PAMAM-modified nano-silica, and the content of the PAMAM-modified nano-silica decreases from the surface to the inside of the self-healing coating. Polyamidoamine (PAMAM) dendrimer is a colorless to light yellow transparent liquid and does not affect the light transmittance of the touch screen. Using nano-silica as a carrier, dendritic polyamidoamine (PAMAM) is grafted onto its surface through covalent bonds to form a stable composite structure. The terminal amino or carboxyl group of PAMAM reacts with the hydroxyl group (-OH) on the surface of silica to achieve chemical anchoring. The dendritic molecules of PAMAM provide a high density of functional groups (such as amino groups, amide groups), which can significantly increase the reaction sites on the surface of silica and serve as the anchoring points for dynamic hydrogen bonds, promoting the rapid recombination of konjac glucomannan molecular chains at the damaged interface and improving the repair efficiency.

[0031] Specifically, the content of PAMAM-modified nano-silica decreases from the surface to the inside of the self-healing coating. Similarly, the self-healing coating of the touch screen can be specifically divided into three layers, and the three sub-layers are formed by curing a mixed sol of PAMAM-modified nano-silica and konjac glucomannan with different concentrations. In this way, the content of PAMAM-modified nano-silica decreases from the surface to the inside of the self-healing coating. The concentration of PAMAM-modified nano-silica on the surface layer of the self-healing coating is relatively high, which can provide more active sites such as amino groups and hydroxyl groups, serving as "anchoring points" for dynamic hydrogen bonds or dynamic chemical bonds, improving the repair strength of the damaged interface, enhancing the repair efficiency, and also increasing the mechanical properties and wear resistance of the surface layer of the self-healing coating.

[0032] According to another aspect of the present invention, the present invention further provides a method for preparing a self-healing coating for a touch screen, comprising the following steps: Add an appropriate amount of konjac glucomannan powder into deionized water and stir evenly, and then divide the formed konjac glucomannan solution into multiple portions; Graft POSS onto the surface of nano-silica to obtain POSS-modified nano-silica; Add different contents of POSS-modified nano-silica to the prepared multiple portions of konjac glucomannan solution in sequence, so as to obtain multiple portions of mixed sols with sequentially increasing concentrations of POSS-modified nano-silica; Coat the multiple portions of mixed sols on the surface of the same touch screen in the order of sequentially increasing concentrations of POSS-modified nano-silica and preliminarily cure to form a multi-layer stacked structure; Make the mixed sol cure to form a self-healing coating through a drying and UV curing process.

[0033] Specifically, take an appropriate amount of konjac glucomannan powder and add it to deionized water and stir evenly to form a konjac glucomannan sol. Divide the obtained konjac glucomannan sol into multiple portions, for example, it can be divided into three portions and stored in three storage buckets respectively, denoted as storage bucket No. 1, storage bucket No. 2, and storage bucket No. 3.

[0034] Graft POSS onto the surface of nano-silica. In a corrosion-resistant reaction kettle, add nano-silica powder and POSS powder according to a mass ratio of 1.2:1, disperse POSS and nano-silica powder in the solvent with ethanol as the solvent, with a solid-liquid ratio of 1:15, add a silane coupling agent (such as KH550, with a dosage of 3-5% of the mass of silica), adjust the pH to 4-5, and stir and react at 70 °C for 4-6 hours to form Si-O-Si covalent bonds. After the reaction is completed, the POSS-modified silica can be dried in a vacuum drying oven.

[0035] The dried POSS-modified silica is added to the obtained konjac glucomannan sol. The concentration of the POSS-modified silica added to each portion of the konjac glucomannan sol is different, and the finally obtained mixed sols are arranged in ascending order of the concentration of the POSS-modified silica. For example, the obtained konjac glucomannan sol is divided into three portions and stored in three storage barrels respectively, denoted as storage barrel No. 1, storage barrel No. 2, and storage barrel No. 3. A predetermined amount of POSS-modified silica is added to the three storage barrels in sequence, so that the concentrations of the POSS-modified silica in storage barrel No. 1, storage barrel No. 2, and storage barrel No. 3 are 2 g / L, 4 g / L, and 6 g / L respectively.

[0036] The multiple portions of the mixed sols are sequentially coated on the surface of the same touch screen in ascending order of the concentration of the POSS-modified nano-silica. For example, a layer of the mixed sol with a predetermined thickness and a concentration of the POSS-modified nano-silica of 2 g / L is first coated on the surface of the touch screen and preliminarily cured; then a layer of the mixed sol with a predetermined thickness and a concentration of the POSS-modified nano-silica of 4 g / L is coated on the surface of the touch screen and preliminarily cured; finally, a layer of the mixed sol with a predetermined thickness and a concentration of the POSS-modified nano-silica of 6 g / L is coated on the surface of the touch screen.

[0037] After the coating of the mixed sol is completed, the touch screen is first placed in a vacuum drying oven for preliminary drying, and then the mixed sol coated on the surface of the touch screen is cured by an ultraviolet curing process to form a self-healing coating.

[0038] In other embodiments, the number of coating layers of the mixed sol on the touch screen can also be two, four, or other numbers.

[0039] For the self-healing coating of the touch screen prepared by the above method, the content of the POSS-modified nano-silica in the coating decreases from the surface to the inside of the self-healing coating. In this way, the content of the POSS-modified nano-silica on the surface layer is relatively high, which can provide more active sites such as amino groups and hydroxyl groups, serving as "anchoring points" for dynamic hydrogen bonds or dynamic chemical bonds, improving the repair strength of the damaged interface and enhancing the repair efficiency. In addition, the high-concentration POSS-modified nano-silica can also increase the mechanical properties and wear resistance of the surface layer of the self-healing coating. The cracks in the inner layer are relatively slight, so the concentration of the POSS-modified nano-silica can be relatively low, and the concentration of the konjac glucomannan can be relatively high, so as to maintain a relatively high light transmittance, toughness, and adhesion, inhibit the cracks from continuing to expand to deeper positions, thereby enhancing the repair strength of the scratches on the touch screen and greatly improving the problem that obvious traces still exist after the scratches in the prior art are repaired. By adopting the above batch-by-batch coating method, a self-healing coating with a gradient distribution of silica concentration can be obtained through simple operation, and the manufacturing cost is relatively lower, without the need for expensive equipment and complex professional operations.

[0040] In one embodiment, POSS is grafted onto the surface of nano-silica to obtain POSS-modified nano-silica, including: Add nano-silica powder into deionized water and perform ultrasonic cleaning to remove impurities and bubbles on the surface of nano-silica; Add nano-silica into tetrafluorohydropyran solvent and stir evenly to form a silica dispersion; Dissolve the silane coupling agent in tetrafluorohydropyran solvent to form a uniform silane coupling agent solution; Dissolve the POSS monomer in tetrafluorohydropyran solvent, and synchronously add it to the silica dispersion together with the silane coupling agent solution. Stir and react at 70 °C for 4 - 6 hours and then dry.

[0041] Specifically, in the grafting modification process of POSS and silica, disperse nano-silica powder in deionized water, and then perform ultrasonic cleaning to remove impurities and bubbles on the surface of silica particles. In addition, the nano-silica can be activated with an acid solution to expose more hydroxyl groups on the nano-silica and improve the subsequent reaction activity. After the treatment is completed, the nano-silica powder is dried by a dryer to remove moisture.

[0042] Then prepare a reaction kettle, add tetrafluorohydropyran solvent into the reaction kettle, and then disperse the pretreated nano-silica in the tetrafluorohydropyran solvent. The solution can be stirred by a stirring device to form a silica dispersion.

[0043] Dissolve the silane coupling agent in tetrafluorohydropyran solvent to form a uniform silane coupling agent solution. For example, KH550 is used, and the dosage is 3 - 5% of the mass of silica.

[0044] Dissolve the POSS monomer in tetrafluorohydropyran solvent, and synchronously add it to the silica dispersion together with the silane coupling agent solution. Adjust the pH of the mixed solution to 4 - 5, stir and react at 70 °C for 4 - 6 hours to graft POSS onto the surface of nano-silica. Finally, put the nano-silica modified by POSS grafting into a vacuum drying oven for drying.

[0045] In the above grafting modification process, tetrafluorohydropyran solvent is used as a single graft coupling agent. A high-polarity solvent (such as tetrafluorohydropyran) can improve the compatibility of POSS and the silane coupling agent, and the grafting rate is relatively high.

[0046] In one embodiment, in the step of grafting POSS onto the surface of nano-silica to obtain POSS-modified nano-silica, the feeding mass ratio of nano-silica to POSS is 1.2:1. After grafting modification with POSS, more active sites can be exposed on the silica. Multiple hydrogen bonds are formed between the hydroxyl groups of konjac glucomannan and the hydroxyl groups on the surface of nano-silica and the organic side chains (such as amino groups) of POSS. When the coating is damaged, the hydrogen bonds break. However, under temperature stimulation, such as heating to 40 °C, the molecular chain movement ability of konjac glucomannan is enhanced, and the broken hydrogen bonds are dynamically reorganized through the reorientation of hydroxyl groups with hydroxyl groups / amino groups, achieving self-healing. When the feeding mass ratio of nano-silica to POSS is 1.2:1, the comprehensive number of active sites of the hydroxyl groups on the surface of nano-silica and the organic side chains of POSS is relatively large, and the effect of rapid self-healing for scratches is relatively ideal.

[0047] In one embodiment, the konjac glucomannan solution is divided into three portions, and POSS-modified nano-silica is sequentially added to the three portions of the konjac glucomannan solution, so that the concentrations of POSS-modified nano-silica in the three mixed sols are 2 g / L, 4 g / L, and 6 g / L respectively; The multiple portions of the mixed sols are sequentially coated on the surface of the touch screen in the order of increasing concentration of POSS-modified nano-silica, including: First, a sol containing POSS-modified nano-silica with a concentration of 2 g / L is coated on the touch screen, and after preliminary curing, a graphene layer is coated; Then, a sol containing POSS-modified nano-silica with a concentration of 4 g / L is coated on the touch screen, and after preliminary curing, a graphene layer is coated; Then, a sol containing POSS-modified nano-silica with a concentration of 6 g / L is coated on the touch screen, and after preliminary curing, a graphene layer is coated; Finally, through drying and UV curing processes, the three-layer mixed sol is cured to form a self-healing coating. In the order from the surface to the inside of the self-healing coating, the thicknesses of the three-layer mixed sol after curing are 50 microns, 30 microns, and 20 microns respectively, and the thickness of the graphene layer is 10 - 15 nanometers.

[0048] In this way, the surface layer contains a relatively high concentration of POSS-modified nano-silica, which can repair relatively severe surface scratches and improve wear resistance and mechanical strength; the concentration of POSS-modified nano-silica in the middle layer is the second, which can repair relatively minor scratches, and as the content of konjac glucomannan increases, the toughness is improved, and it can inhibit the scratches from continuing to spread towards the deep layer; the concentration of POSS-modified nano-silica in the innermost layer is the lowest, and the content of konjac glucomannan is the highest, so that the substrate of the self-healing coating maintains a relatively high light transmittance and toughness. Secondly, in the order from the surface to the inside of the self-healing coating, the thicknesses of the three layers after sol curing are 50 microns, 30 microns, and 20 microns respectively. In this way, not only the content of POSS-modified nano-silica in the outermost layer is the highest, but also the thickness is the thickest; while the innermost layer has the lowest content of POSS-modified nano-silica and the thinnest thickness, thus further optimizing the gradient change of the content of POSS-modified nano-silica in the self-healing coating, so that POSS-modified nano-silica is distributed as much as possible in the outer layer of the self-healing coating, increasing the repair ability and effect of the surface layer of the self-healing coating.

[0049] In addition, by coating a graphene layer between two adjacent cured sols, as a two-dimensional material, graphene can form a continuous film by solution spraying, so as to combine with the sol curing layer. The graphene layer can provide conductivity and mechanical support, and can improve the sensitivity and durability of the touch screen; moreover, the hardness of the graphene layer is greater than that of the cured sol, so such a self-healing coating forms a "soft-hard-soft" alternating structure. The graphene layer can inhibit the crack propagation of the self-healing coating during sliding friction and reduce the interlayer stress concentration. Especially, the layered structure of graphene can inhibit the longitudinal propagation of cracks towards deeper depths, thereby extending the service life.

[0050] Particularly, the thickness of the graphene layer is 10 - 15 nanometers. When the thickness of the graphene layer exceeds 20 nanometers, the light transmittance decreases significantly (<85%), which may affect the screen display effect. While a graphene layer with a thickness of 10 - 15 nanometers can not only meet the requirements of the touch screen for conductivity, but also improve the fracture toughness, maintain a good mechanical strengthening effect, and effectively prevent crack propagation across layers through the two-dimensional sheet structure.

[0051] In one embodiment, the graphene layer is formed by coating through the following steps: Disperse graphene in deionized water, add sodium dodecyl sulfate as a surfactant, form a dispersion by ultrasonic treatment, and then spray to form a film layer with a thickness of 10 - 15 nanometers.

[0052] Sodium dodecyl sulfate, as an anionic surfactant, has its hydrophobic end (dodecyl chain) adsorbed on the surface of graphene through van der Waals forces, and its hydrophilic end (sulfate group) extends into the water, forming a double electric layer (enhanced Zeta potential), which effectively inhibits the stacking of graphene sheets through π-π bonds or agglomeration through van der Waals forces. Through ultrasonic dispersion treatment, the dispersion of single-layer or few-layer graphene is achieved. The ultrasonic atomization spraying technology can be used to accurately control the droplet size, making the film thickness uniform. The 10 - 15 nm film layer has both high transparency (visible light region > 90%) and excellent conductivity (sheet resistance < 100 Ω / sq). In one embodiment, the method for preparing the self-healing coating of the touch screen further includes the following steps: Graft PAMAM onto the surface of nano-silica to obtain PAMAM-modified nano-silica. Add different contents of PAMAM-modified nano-silica to multiple prepared konjac glucomannan solutions in sequence, so that in each konjac glucomannan solution, the mass ratio of POSS-modified nano-silica to PAMAM-modified nano-silica is 1:1.

[0053] Specifically, when grafting POSS onto the surface of nano-silica to obtain POSS-modified nano-silica, PAMAM can be simultaneously grafted onto the surface of nano-silica to obtain PAMAM-modified nano-silica. Then add two components, POSS-modified nano-silica and PAMAM-modified nano-silica, to the konjac glucomannan solution simultaneously. In each konjac glucomannan solution, the mass of POSS-modified nano-silica and PAMAM-modified nano-silica is the same. That is to say, in the konjac glucomannan solution with a lower concentration of POSS-modified nano-silica added, the concentration of PAMAM-modified nano-silica added is also lower; while in the konjac glucomannan solution with a higher concentration of POSS-modified nano-silica added, the concentration of PAMAM-modified nano-silica added is also higher. The terminal amino group of PAMAM (polyamide-amine dendrimer) can achieve rapid self-healing through dynamic covalent bonds (such as imine bonds), and in the scratch experiment, the PAMAM grafting system can complete the repair at room temperature. In addition, the dendritic structure of PAMAM can adsorb more nano-silica particles, forming a multi-level dispersion network, and the fracture toughness of the coating is increased by 15%. This ensures that the surface layer of the self-healing coating always has more active sites relative to the inner layer, which can serve as the "anchoring points" of dynamic hydrogen bonds or dynamic chemical bonds, improving the repair strength of the damaged interface, enhancing the repair efficiency, and also increasing the mechanical properties and wear resistance of the surface layer of the self-healing coating.

[0054] In one embodiment, the following steps are further included: adding silver nanowires to the konjac glucomannan solution. Specifically, after dissolving konjac glucomannan in deionized water to form a konjac glucomannan solution, silver nanowires are added to the konjac glucomannan solution. On the one hand, this can increase the conductivity of the self-healing coating of the subsequent formed touch screen and improve the touch sensitivity of the touch screen; on the other hand, silver nanowires also have certain antibacterial properties, so that the self-healing coating of the formed touch screen also has certain antibacterial properties and becomes a multifunctional composite coating. Embodiment

[0055] A method for preparing a self-healing coating of a touch screen is prepared by the following steps: Add an appropriate amount of konjac glucomannan powder to deionized water and stir evenly to form a konjac glucomannan solution, then add silver nanowires to the konjac glucomannan solution, and divide the solution into three equal parts; Add nano-silica powder to deionized water and perform ultrasonic cleaning to remove impurities and bubbles on the surface of nano-silica; then add nano-silica to the tetrafluorohydran solvent and stir evenly to form a silica dispersion; dissolve the silane coupling agent in the tetrafluorohydran solvent to form a uniform silane coupling agent solution; dissolve the POSS monomer and PAMAM monomer in the tetrafluorohydran solvent according to a mass ratio of 1:1, and synchronously add them to the silica dispersion with the silane coupling agent solution. The feeding mass ratio of nano-silica and POSS is 1.2:1. After stirring and reacting at 70 °C for 4-6 hours, dry to obtain POSS and PAMAM mixed-modified nano-silica; Sequentially add different contents of the mixed-modified nano-silica to the three prepared konjac glucomannan solutions, so that the concentrations of the mixed-modified nano-silica in the three mixed sols are 2 g / L, 4 g / L, and 6 g / L respectively; Coat the three mixed sols on the surface of the same touch screen in the order of increasing concentration of the mixed-modified nano-silica and preliminarily cure them into a three-layer stacked structure; The mixed sol is cured by drying and UV curing processes to form a self-healing coating.

[0056] Three samples were prepared by the above method and were respectively denoted as sample a, sample b, and sample c. A commercially available touch screen with a self-healing coating was used as a control sample. Under the environment of 25°C and 45% humidity, with the same scratch force (scratched by a 500 g weight), the scratch depth was 10 - 15 μm, and the effect of single scratch repair, the time required for repair, the scratch depth before and after repair, the scratch repair rate, and the roughness before and after repair were recorded. In addition, all samples were subjected to 150 scratch-repair cycle tests, the transmittance (visible light band) after 150 repairs was recorded, and the light transmittance retention rate was calculated. The results are shown in Table 1 below: Table 1 Self-healing performance test data of three samples and the control sample

[0057] In summary, the present application provides a self-healing coating for a touch screen. The self-healing coating is formed by curing a sol formed by konjac glucomannan and POSS-modified nano-silica. The content of the POSS-modified nano-silica decreases from the surface to the inside of the self-healing coating. Thus, for the surface layer with relatively severe scratches, the self-healing strength and efficiency are improved by the relatively high concentration of POSS-modified nano-silica, and at the same time, the mechanical properties and wear resistance of the surface layer are improved; for the inner layer with minor cracks, the concentration of konjac glucomannan is relatively higher, so as to maintain a relatively high transmittance, toughness, and adhesion, and inhibit the cracks from continuing to expand to deeper positions. The self-healing coating of the touch screen is formed by curing a mixed sol containing different concentrations of konjac glucomannan by batch coating, with simple operation and low cost.

[0058] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A self-repairing coating for a touch screen, characterized in that: The self-repairing coating is formed by solidifying a sol formed by konjac glucomannan and POSS-modified nano-silica, wherein the content of the POSS-modified nano-silica decreases from the surface of the self-repairing coating to the inside. The self-repairing coating is a multilayer stacked structure formed by sequentially coating the sol containing different concentrations of the POSS-modified nano-silica on the surface of the touch screen and solidifying.

2. The self-repairing coating for a touch screen according to claim 1, characterized in that: The self-healing coating is formed by solidifying three layers of sol, and a graphene layer is coated between each two adjacent layers of solidified sol, and the thickness of the graphene layer is 10-15 nanometers; in order from the surface of the self-healing coating to the inside, the concentrations of the POSS modified nano-silica contained in the three layers of sol before solidification are 6g / L, 4g / L, and 2g / L, respectively, and the thicknesses of the three layers of sol after solidification are 50 microns, 30 microns, and 20 microns, respectively.

3. The self-repairing coating for a touch screen according to claim 1 or 2, characterized in that: The self-repairing coating further comprises PAMAM-modified nano-silicon dioxide, and the content of the PAMAM-modified nano-silicon dioxide decreases from the surface of the self-repairing coating toward the inside.

4. A method for preparing a self-repairing coating for a touch screen, characterized in that: include: Add an appropriate amount of konjac glucomannan powder into deionized water and stir evenly, then divide the formed konjac glucomannan solution into multiple portions; Grafting POSS onto the surface of nano-silica to obtain POSS-modified nano-silica; Sequentially adding different contents of POSS-modified nano-silica to the prepared multiple konjac glucomannan solutions, thereby obtaining multiple mixed sols with successively increasing concentrations of POSS-modified nano-silica; In the order of increasing concentration of POSS-modified nano-silica, multiple mixed sols are coated on the surface of the same touch screen and initially cured to form a multi-layer stacking structure; The mixed sol is cured through drying and UV curing process to form a self-healing coating.

5. The method for preparing the self-repairing coating of the touch screen according to claim 4, characterized in that: Grafting POSS onto the surface of nano-silica to obtain POSS-modified nano-silica, including: Adding nano-silicon dioxide powder into deionized water and performing ultrasonic cleaning to remove impurities and bubbles on the surface of the nano-silicon dioxide; Adding nano-silicon dioxide into tetrafluoroethylene solvent and stirring evenly to form a silicon dioxide dispersion; Dissolving the silane coupling agent in tetrafluoroethylene solvent to form a uniform silane coupling agent solution; The POSS monomer was dissolved in tetrafluoroethylene solvent and added into the silica dispersion simultaneously with the silane coupling agent solution. The mixture was stirred at 70° C. for 4-6 hours and then dried.

6. The method for preparing the self-repairing coating of the touch screen according to claim 5, characterized in that: When POSS is grafted onto the surface of nano-silica to prepare POSS-modified nano-silica, the feed mass ratio of nano-silica to POSS is 1.2:

1.

7. The method for preparing a self-repairing coating for a touch screen according to claim 4, characterized in that: The konjac glucomannan solution is divided into three parts, and POSS modified nano silicon dioxide is added to the three parts of konjac glucomannan solutions in sequence, so that the concentrations of POSS modified nano silicon dioxide in the three parts of mixed sols are 2g / L, 4g / L, and 6g / L respectively; The method comprises coating the plurality of mixed sols on the surface of the touch screen in the order of increasing concentration of POSS-modified nano-silicon dioxide, including: First, a layer of sol containing POSS-modified nano-silica with a concentration of 2 g / L is coated on the touch screen, and then a layer of graphene is coated after preliminary curing; Then, a layer of sol containing POSS-modified nano-silica with a concentration of 4 g / L is coated on the touch screen, and after preliminary curing, a layer of graphene is coated; Then, a layer of sol containing POSS-modified nano-silica with a concentration of 6 g / L is coated on the touch screen, and after preliminary curing, a layer of graphene is coated; Finally, the three layers of mixed sol are cured through drying and UV curing process to form a self-healing coating. In order from the surface of the self-healing coating to the inside, the thickness of the three layers of mixed sol after curing is 50 microns, 30 microns, and 20 microns, respectively, and the thickness of the graphene layer is 10-15 nanometers.

8. The method for preparing the self-repairing coating of the touch screen according to claim 7, characterized in that: The graphene layer is formed by coating through the following steps: The graphene is dispersed in deionized water, and sodium dodecyl sulfate is added as a surfactant. The dispersion is formed by ultrasonic treatment and then sprayed to form a film layer with a thickness of 10-15 nanometers.

9. The method for preparing a self-repairing coating for a touch screen according to any one of claims 4 to 8, characterized in that: The following steps are also included: PAMAM is grafted onto the surface of nano-silica to prepare PAMAM-modified nano-silica, and different contents of PAMAM-modified nano-silica are sequentially added to the prepared multiple konjac glucomannan solutions, so that in each konjac glucomannan solution, the mass ratio of POSS-modified nano-silica to PAMAM-modified nano-silica is 1:

1.

10. The method for preparing the self-repairing coating of a touch screen according to claim 9, characterized in that: The following steps are also included: Adding nanosilver wires into the konjac glucomannan solution.

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