A high-transparency, high-surface-hardness and bendable coating layer and a preparation method thereof

Abstract

This invention discloses a method for preparing a highly transparent, high-surface-hard, and bendable coating, comprising the following specific steps: Step 1, mixing nanoparticles, a curable organic mixture, and an initiator to prepare a hard coating layer; mixing the curable organic mixture and the initiator to prepare a soft coating layer; Step 2, applying the soft coating layer to a substrate surface and subjecting it to photocuring or thermal curing treatment, thereby obtaining a pre-cured soft layer that is not fully cured by controlling the curing time; Step 3, applying a hard coating layer onto the pre-cured soft layer and subjecting it to photocuring or thermal curing treatment. The coating structure obtained by the preparation method of this invention sequentially includes a soft layer, a gradient layer, and a hard layer, simultaneously possessing high surface hardness, excellent bend resistance, and high transparency, solving the technical problem that traditional coating manufacturing processes cannot simultaneously achieve both surface hardness and bend resistance.

Description

Technical Field

[0001] This invention relates to the field of coating preparation, and in particular to a highly transparent, high-surface-hardness, and bendable coating and its preparation method. Background Technology

[0002] In recent years, electronic devices have been developing towards flexibility and foldability. Major companies and academic institutions have continuously launched foldable displays and foldable smartphones, subverting the traditional display design concept and heralding the arrival of the flexible electronics era. A typical foldable display usually consists of a cover plate (or surface coating), a touch-sensing layer, a front panel, and a display back panel. Among them, the cover plate (or surface coating) material needs to simultaneously meet requirements such as bendability, high transparency, and high surface hardness. The high technical barriers and manufacturing difficulties are one of the key issues restricting the commercialization of foldable screens.

[0003] Traditional displays typically use glass as the cover material to increase the surface hardness of the screen. However, glass has a high modulus, is not easily bent, and is fragile, making it difficult to be an ideal solution to this problem. While plastic materials have excellent flexibility, their low hardness makes them unsuitable for practical applications and also fails to effectively solve the aforementioned issues.

[0004] Due to the inherent contradiction between a material's bending ability and high hardness, traditional coating preparation processes struggle to create coatings that combine high transparency, flexibility, and high hardness. While a few existing coatings can achieve a degree of surface hardness and bendability, both are less than ideal, and their preparation processes are cumbersome, complex, and costly, hindering their widespread adoption.

[0005] Therefore, there is an urgent need to provide a coating preparation method that can balance or control the contradiction between the flexibility and surface hardness of transparent coatings and is simple and efficient. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art by providing a highly transparent, high-surface-hardness, and bendable coating and its preparation method.

[0007] The objective of this invention is achieved through the following technical solution: a method for preparing a highly transparent, high-surface-hard, and bendable coating, comprising the following specific steps:

[0008] Step 1: Prepare a hard coating by mixing nanoparticles, a curable organic mixture, and an initiator; prepare a soft coating by mixing the curable organic mixture and an initiator. Step 2: Apply the soft coating to the substrate surface and perform photocuring or heat curing treatment. By controlling the curing time, a pre-cured soft layer that is not fully cured is obtained. Step 3: Apply a hard coating onto the pre-cured soft layer and perform photocuring or heat curing to ensure that the upper part of the hard coating is completely cured to form a hard layer and the lower part of the pre-cured soft layer is formed a soft layer. Through the penetration between the hard coating and the soft coating, a gradient layer is spontaneously formed between the soft layer and the hard layer. The gradient layer is a gradient distribution structure formed by the hard coating components and the soft coating components.

[0009] Preferably, the coating method for the soft coating and the hard coating is selected from any one of drip coating, spin coating, bar coating, scraping coating, dip coating, and spray coating.

[0010] Preferably, the initiator is a photoinitiator or a thermal initiator, and the mass percentage of the initiator in the soft coating and the hard coating is 1 to 10%.

[0011] Preferably, the photoinitiator is selected from 2 hydroxyl 2 methyl phenyl acetone, 1 Hydroxycyclohexylphenyl ketone, phenylbis(2,4,6) Trimethylbenzoyl)phosphine oxide, 2 hydroxyl 2 methyl 1 [4 (2 [hydroxyethoxy)phenyl] 1 Acetone, benzoin dimethyl ether, triphenylthionium hexafluoroantimonate or 2,2-dimethyl benzoate At least one of diethoxyacetophenone; The thermal initiator is selected from at least one of azo initiators, peroxide initiators, organotin compounds, chloroplatinic acid, (Ph3P)4Pd, [RhCl(CO)2]2, and organic bases; the azo initiator is selected from one of azobisisobutyronitrile, azobisisobutyramidine hydrochloride, and azobisisopropylimidazoline hydrochloride; the peroxide initiator is selected from one of benzoyl peroxide, tert-butyl peroxide, and methyl ethyl ketone peroxide.

[0012] Preferably, the surface of the nanoparticles is grafted with reactive functional groups, which are introduced by grafting with a silane coupling agent; the curable organic mixture is at least one of monofunctional olefins and polyfunctional olefins containing carbon-carbon double bonds; the reactive functional groups on the surface of the inorganic oxide nanoparticles undergo addition polymerization with the curable organic mixture.

[0013] Preferably, the monofunctional olefin is selected from at least one of methyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, polyethylene glycol monoacrylate, siloxane acrylate, and 4-acryloylmorpholine; the polyfunctional olefin is selected from at least one of bisphenol A acrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and epoxy acrylate.

[0014] Preferably, the nanoparticles are selected from one of silicon dioxide, aluminum oxide, titanium dioxide, and zirconium oxide.

[0015] Preferably, the thermosetting treatment method is to cure at a temperature of 50-200℃ for a curing time of 1s-120min; the photocuring treatment method is to cure by ultraviolet light irradiation for a curing time of 1s-120min.

[0016] A highly transparent, high-surface-hardness, and bendable coating comprises, from bottom to top, a substrate, a soft layer, a gradient layer, and a hard layer. During the pre-curing stage, the soft layer coating penetrates the hard layer coating to spontaneously form a gradient layer, which is a gradient distribution structure formed by the hard layer coating components and the soft layer coating components. Along the direction away from the hard layer, the content of the hard layer coating components in the gradient layer gradually decreases while the content of the soft layer coating components gradually increases.

[0017] Preferably, the overall thickness of the coating is 10-300 μm, and the thickness of the gradient layer is 200 nm-1 μm.

[0018] The beneficial effects of this invention are: 1. The coating structure prepared by the method of the present invention comprises, in sequence, a soft layer, a gradient layer, and a hard layer. The uppermost hard layer provides extremely high surface hardness and scratch and wear resistance. The high hardness of the coating surface is achieved by controlling the filling and curing system of nanoparticles in the hard layer coating. Its surface hardness far exceeds that of traditional flexible coatings, solving the problem of insufficient surface hardness and easy scratching of traditional flexible coatings, and meeting the wear resistance requirements of daily use of consumer electronic products such as foldable screens. The bottommost soft layer provides excellent flexibility and bending stress absorption, giving the coating superior bending resistance. It can withstand tens of thousands or even hundreds of thousands of repeated bends at extremely small bending radii without cracking or failure, solving the problem of high-hardness glass or hard coatings being brittle and easily broken when bent. The gradient layer, as a key structural layer balancing the entire coating, forms a gradient structure of composition and modulus through the spontaneous interpenetration of soft and hard coatings. This eliminates the obvious hard-soft interface of traditional multilayer composite coatings, achieving a uniform transition between soft and hard layers. It avoids stress concentration at the interface during bending, and achieves smooth transmission and slow release of bending stress. It will not cause interlayer peeling or cracking due to poor interface bonding, nor will it cause hard layer brittleness due to stress concentration. At the same time, it has high surface hardness, excellent bending resistance, and high transparency, solving the technical problem that traditional coating manufacturing processes cannot simultaneously achieve both surface hardness and bending resistance.

[0019] 2. The preparation process of the present invention is simple and has no additional complex steps. The preparation process can be completed by conventional coating, light or heat curing. There is no need for high-end complex equipment and processes such as vacuum evaporation and plasma treatment. The gradient layer is spontaneously formed by the penetration of the coating. The gradient layer structure can be constructed without additional process steps. The production process is greatly simplified, the production efficiency is improved, and the preparation cost is greatly reduced, which is conducive to large-scale promotion and use.

[0020] 3. In the actual preparation process, by adjusting the pre-curing time of the soft layer, the curing degree of the soft layer can be controlled, thereby precisely regulating the penetration degree and depth between the soft and hard coating layers. This allows for the control of the thickness, component distribution, and modulus gradient of the gradient layer. Furthermore, by adjusting the formulation of the soft and hard coating layers, different hardness and bending performance requirements can be flexibly adapted without significantly altering the production process, demonstrating strong adaptability. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the preparation process of the present invention.

[0022] Figure 2 This is an electron microscope (EM) structural diagram of the coating of the present invention.

[0023] Figure 3 The image shows the UV-Vis transmittance curves of the coatings prepared in Examples 2 and 3 of this invention.

[0024] Figure 4 This is a nanoindentation test image of the coating prepared in Example 1 of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0026] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0027] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0028] like Figure 1 As shown, a method for preparing a highly transparent, high-surface-hard, and bendable coating includes the following specific steps: Step 1: Prepare a hard coating by mixing nanoparticles, a curable organic mixture, and an initiator; prepare a soft coating by mixing the curable organic mixture and an initiator. Step 2: Apply the soft coating to the substrate surface and perform photocuring or heat curing treatment. By controlling the curing time, a pre-cured soft layer that is not fully cured is obtained. Step 3: Apply a hard coating onto the pre-cured soft layer and perform photocuring or heat curing to ensure that the upper part of the hard coating is completely cured to form a hard layer and the lower part of the pre-cured soft layer is formed a soft layer. Through the penetration between the hard coating and the soft coating, a gradient layer is spontaneously formed between the soft layer and the hard layer. The gradient layer is a gradient distribution structure formed by the hard coating components and the soft coating components.

[0029] The semi-cured state of the soft layer (pre-cured) relies on the role of oxygen in inhibiting polymerization during the curing process. In actual experiments, during photocuring, ambient oxygen affects the curing process, preventing curing. Consequently, the portion of the soft layer surface in contact with oxygen remains largely uncured, while the bottommost layer, furthest from oxygen, is the most cured. Therefore, in the cross-sectional direction, the closer to the surface, the less cured the layer.

[0030] The curing state of the soft layer can be controlled by the curing time; the longer the curing time, the higher the overall degree of curing. Furthermore, the curing state can also be controlled by adjusting the oxygen content in the environment; the lower the oxygen content, the higher the overall degree of curing. In a completely oxygen-free environment, complete curing can be achieved rapidly.

[0031] The coating structure prepared by the method of the present invention comprises, in sequence, a soft layer, a gradient layer, and a hard layer. The uppermost hard layer provides extremely high surface hardness and scratch and wear resistance. The high surface hardness of the coating is achieved through nanoparticle filling and curing system control, far exceeding that of traditional flexible coatings. This solves the problem of insufficient surface hardness and susceptibility to scratches in traditional flexible coatings, meeting the wear resistance requirements of daily use in consumer electronics products such as foldable screens.

[0032] The bottom soft layer provides excellent flexibility and bending stress absorption capacity, giving the coating excellent bending resistance. It can withstand tens of thousands or even hundreds of thousands of repeated bends at a very small bending radius without cracking or failure, solving the problem of high-hardness glass or hard coatings being brittle and easily broken when bent.

[0033] As a key structural layer balancing the entire coating, the gradient layer forms a gradient structure of composition and modulus through the spontaneous interpenetration of soft and hard coating layers. This eliminates the obvious hard-soft interface of traditional multilayer composite coatings, achieves a uniform transition between soft and hard layers, avoids stress concentration at the interface during bending, and realizes smooth transmission and slow release of bending stress. It will not cause interlayer peeling or cracking due to poor interface bonding, nor will it cause hard layer brittleness due to stress concentration. At the same time, it has high surface hardness, excellent bending resistance, and high transparency, solving the technical problem that traditional coating manufacturing processes cannot take into account both surface hardness and bending resistance.

[0034] The preparation process of this invention is simple and has no additional complex steps. The preparation process can be completed by conventional coating, light or heat curing. There is no need for high-end complex equipment and processes such as vacuum evaporation and plasma treatment. The gradient layer is spontaneously formed by the penetration of the coating. The gradient layer structure can be constructed without additional process steps, which greatly simplifies the production process, improves production efficiency, and greatly reduces the preparation cost, which is conducive to large-scale promotion and use.

[0035] In the actual preparation process, by adjusting the pre-curing time of the soft layer, the degree of curing of the soft layer can be controlled, thereby precisely regulating the penetration degree and depth between the soft and hard coating layers. This, in turn, regulates the thickness, component distribution, and modulus gradient of the gradient layer. At the same time, by adjusting the formulation of the soft and hard coating layers, different hardness and bending performance requirements can be flexibly adapted without significantly changing the production process, making it highly adaptable.

[0036] The application method for both soft and hard coatings can be selected from any one of the following: drip coating, spin coating, rod coating, scraping coating, dip coating, and spray coating.

[0037] The initiator is a photoinitiator or a thermal initiator, and the mass percentage of the initiator in the soft coating and the hard coating is 1 to 10%.

[0038] Among them, the photoinitiator is selected from 2 hydroxyl 2 methyl phenyl acetone, 1 Hydroxycyclohexylphenyl ketone, phenylbis(2,4,6) Trimethylbenzoyl)phosphine oxide, 2 hydroxyl 2 methyl 1 [4 (2 [hydroxyethoxy)phenyl] 1 Acetone, benzoin dimethyl ether, triphenylthionium hexafluoroantimonate or 2,2-dimethyl benzoate At least one of diethoxyacetophenone; the thermal initiator is selected from at least one of azo initiators, peroxide initiators, organotin compounds, chloroplatinic acid, (Ph3P)4Pd, [RhCl(CO)2]2, and organic bases; the azo initiator is selected from one of azobisisobutyronitrile, azobisisobutyramidine hydrochloride, and azobisisopropylimidazoline hydrochloride; the peroxide initiator is selected from one of benzoyl peroxide, tert-butyl peroxide, and methyl ethyl ketone peroxide.

[0039] The nanoparticles have reactive functional groups grafted onto their surface, which are introduced via silane coupling agents. The curable organic mixture is at least one of a monofunctional olefin or a polyfunctional olefin containing carbon-carbon double bonds. The reactive functional groups on the surface of the inorganic oxide nanoparticles undergo addition polymerization with the curable organic mixture. The addition polymerization reaction includes addition reactions involving carbon-carbon double bonds.

[0040] When traditional inorganic nanoparticles are directly added to organic resin systems, they are prone to agglomeration due to poor compatibility at the inorganic-organic interface. This not only causes light scattering, leading to a decrease in coating transmittance and a surge in haze, but also creates localized stress concentration points, resulting in uneven coating hardness and easy cracking and failure when bent.

[0041] To address the aforementioned problems, this invention utilizes silane coupling agents to perform surface functionalization modification on nanoparticles. The siloxane groups of silane coupling agents can form stable chemical bonds with the hydroxyl groups on the surface of inorganic oxide nanoparticles. The reactive functional groups (containing carbon-carbon double bonds) introduced at the other end can transform the surface of the nanoparticles from inorganic hydrophilic properties to lipophilic properties compatible with organic olefin systems. This significantly improves the compatibility and dispersibility of nanoparticles in curable organic mixtures, achieving monodispersity and nanoscale uniform dispersion of nanoparticles in coating systems. This fundamentally solves the light scattering problem caused by particle agglomeration, ensuring high light transmittance (≥90%) and extremely low haze of the coating. Furthermore, the uniformly dispersed nanoparticles can form a globally uniform mechanically reinforcing phase after curing, avoiding localized excessively high or low hardness and stress concentration defects caused by agglomeration.

[0042] Furthermore, during the preparation process of this invention, a gradient layer needs to be spontaneously formed through the mutual penetration of soft and hard coatings. The grafted and modified nanoparticles have excellent compatibility with the organic olefin system of the soft layer, and can penetrate into the pre-cured soft layer uniformly and smoothly along with the hard coating. This avoids the problem of nanoparticles agglomerating at the interface between the soft and hard layers and being unable to penetrate, ensuring a continuous and smooth gradient distribution of nanoparticles and organic components within the gradient layer. This achieves a gradual change in modulus and refractive index without abrupt changes, further eliminating interface reflection and stress concentration between the soft and hard layers. Bending stress can be smoothly transmitted and slowly released throughout the coating, significantly improving the bending limit and fatigue resistance of the coating.

[0043] The monofunctional olefin is selected from at least one of methyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, polyethylene glycol monoacrylate, siloxane acrylate, and 4-acryloylmorpholine; the polyfunctional olefin is selected from at least one of bisphenol A acrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and epoxy acrylate.

[0044] The nanoparticles are selected from one of silicon dioxide, aluminum oxide, titanium dioxide, and zirconium oxide.

[0045] In some embodiments of this application, the nanoparticles are selected from silicon dioxide.

[0046] In the preparation process of this application, the thermosetting treatment method is: curing at a temperature of 50-200℃ for a curing time of 1s-120min; the photocuring treatment method is: curing by ultraviolet light irradiation for a curing time of 1s-120min.

[0047] A highly transparent, high-surface-hardness, and bendable coating is obtained by the above preparation method. Its structure, from bottom to top, includes a substrate, a soft layer, a gradient layer, and a hard layer. During the pre-curing stage, the soft layer coating penetrates the hard layer coating to spontaneously form a gradient layer. The gradient layer is a gradient distribution structure formed by the hard layer coating components and the soft layer coating components. Along the direction away from the hard layer, the content of the hard layer coating components in the gradient layer gradually decreases while the content of the soft layer coating components gradually increases.

[0048] The overall thickness of the coating is 10-300 μm, and the thickness of the gradient layer is 200 nm-1 μm.

[0049] The coating structure of this invention can be found in [reference needed]. Figure 2 , Figure 2 This is an electron microscope (EM) structural diagram of the coating of the present invention.

[0050] The coating obtained by this invention has a light transmittance of over 90% (wavelength 550nm), high surface hardness, an inward bending radius of less than 1mm, and an outward bending radius as low as 5mm. Furthermore, the coating cures rapidly. In other words, the coating with a gradient layer structure obtained by this invention has high light transmittance, high hardness, good flexibility, a wide adjustable range for hardness and flexibility, and can be fabricated on a large scale using ultrafast methods.

[0051] The following are some specific preparation examples of the present invention.

[0052] Example 1: First, silane coupling agent-grafted KH570-grafted nano-silica (KSiO2, 6g) was added to 60mL of ethanol and stirred at room temperature for dispersion. Then, pentaerythritol triacrylate (PETA, 6g) was added. After removing the ethanol by rotary evaporation, 0.5wt% of photoinitiator 1173 (2 hydroxyl 2 Methylphenylacetone) and 1 wt% photoinitiator TPO (phenylbis(2,4,6) (Trimethylbenzoyl)phosphine oxide) was stirred for five minutes to obtain a hard coating. The product, then used as a soft coating, was spin-coated onto a substrate and cured under 365 nm UV light for 20 seconds. The hard coating was then spin-coated onto the pre-cured soft layer and cured under a mercury lamp for 5 seconds, resulting in a coating material with a hardness H of 818 MPa, an inward bending radius of less than 1 mm, and a light transmittance of 91% (550 nm).

[0053] Among them, the products used as flexible coatings are a mixture of ACMO (4-acryloylmorpholine), polycaprolactone epoxy acrylate oligomer, bisphenol A epoxy acrylate, trimethylolpropane triacrylate, and 2-acrylate (1-methylethylidene) bis(4,1-phenyleneoxy-2,1-ethylenedimethyl) ester (CAS: 24447-78-7).

[0054] The surface hardness of the coating prepared in Example 1 was tested, and the test results are as follows: Figure 4 As shown, Figure 4 For nanoindentation test patterns, by Figure 4 It is known that the surface hardness is 818 MPa; it has excellent surface hardness.

[0055] Example 2: First, KSiO2 (6g) was added to 60mL of ethanol and stirred at room temperature to disperse it. Then, pentaerythritol triacrylate (PETA, 6g) was added. After removing the ethanol by rotary evaporation, 0.5wt% of photoinitiator 1173 (2g) was added. hydroxyl 2 Methylphenylacetone) and 1 wt% photoinitiator TPO (phenylbis(2,4,6) (Trimethylbenzoyl)phosphine oxide) was added to 0.72g of ethanol and stirred for five minutes to obtain a hard coating. Then, product 409, used as a soft coating, was spin-coated onto the substrate and cured under 365nm ultraviolet light for 20 seconds. The hard coating mixture was then spin-coated onto the pre-cured soft layer, and after the solvent evaporated, it was cured under a mercury lamp for 5 seconds to obtain a coating material with a hardness H of 645MPa, an inward bending radius of less than 1mm, an outward bending radius of 5mm, and a light transmittance of 92% (550nm).

[0056] Example 3: First, KSiO2 (6g) was added to 60mL of ethanol and stirred at room temperature to disperse it. Then, pentaerythritol triacrylate (PETA, 4g) was added. After removing the ethanol by rotary evaporation, 0.5wt% of photoinitiator 1173 (2g) was added. hydroxyl 2 Methylphenylacetone) and 1 wt% photoinitiator TPO (phenylbis(2,4,6) (Trimethylbenzoyl)phosphine oxide), stirred for five minutes, to obtain a hard coating. Then, the product, used as a soft coating, is spin-coated onto the substrate and cured under 365nm ultraviolet light for 20 seconds. The hard coating is then spin-coated onto the soft coating and cured under mercury lamp irradiation for 5 seconds, resulting in a coating material with a hardness H of 828MPa, an inward bending radius of less than 1mm, and a light transmittance of 91% (550nm).

[0057] The transmittance of the coatings prepared in Examples 2 and 3 was tested, and the results are as follows: Figure 3 As shown. Figure 3 The UV-Vis transmittance curves for the coatings prepared in Examples 2 and 3 are shown. Figure 3 It can be seen that the highly transparent, rigid and flexible coatings with gradient layer structures prepared by Examples 2 and 3 have excellent light transmittance, reaching over 91% (wavelength of 550nm).

[0058] Example 4: First, KSiO2 (6g) was added to 60mL of ethanol and stirred at room temperature to disperse it. Then, pentaerythritol triacrylate (PETA, 4g) was added. After removing the ethanol by rotary evaporation, 0.5wt% of photoinitiator 1173 (2g) was added. hydroxyl 2 Methylphenylacetone) and 1 wt% photoinitiator TPO (phenylbis(2,4,6) (Trimethylbenzoyl)phosphine oxide) was added to 0.5g of ethanol and stirred for five minutes to obtain a hard coating. The product, used as a soft coating, was then spin-coated onto a substrate and cured under 365nm UV light for 20 seconds. The hard coating mixture was then spin-coated onto the pre-cured soft layer, and after solvent evaporation, cured under a mercury lamp for 5 seconds to obtain a coating material with a hardness H of 846MPa, an inward bending radius of less than 1mm, an outward bending radius of 6mm, and a light transmittance of 91% (550nm).

[0059] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for preparing a highly transparent, high-surface-hard, and bendable coating, characterized in that, The specific steps include the following: Step 1: Prepare a hard coating by mixing nanoparticles, a curable organic mixture, and an initiator; prepare a soft coating by mixing the curable organic mixture and an initiator. Step 2: Apply the soft coating to the substrate surface and perform photocuring or heat curing treatment. By controlling the curing time, a pre-cured soft layer that is not fully cured is obtained. Step 3: Apply a hard coating onto the pre-cured soft layer and perform photocuring or heat curing to ensure that the upper part of the hard coating is completely cured to form a hard layer and the lower part of the pre-cured soft layer is formed a soft layer. Through the penetration between the hard coating and the soft coating, a gradient layer is spontaneously formed between the soft layer and the hard layer. The gradient layer is a gradient distribution structure formed by the hard coating components and the soft coating components.

2. The method for preparing a highly transparent, high-surface-hard, and bendable coating according to claim 1, characterized in that, The application method for the soft coating and the hard coating is selected from any one of the following: drip coating, spin coating, bar coating, scraping coating, dip coating, and spray coating.

3. The method for preparing a highly transparent, high-surface-hardness, and bendable coating according to claim 1, characterized in that, The initiator is a photoinitiator or a thermal initiator, and the mass percentage of the initiator in the soft coating and the hard coating is 1 to 10%.

4. The method for preparing a highly transparent, high-surface-hardness, and bendable coating according to claim 3, characterized in that, The photoinitiator is selected from 2 hydroxyl 2 methyl phenyl acetone, 1 Hydroxycyclohexylphenyl ketone, phenylbis(2,4,6) Trimethylbenzoyl)phosphine oxide, 2 hydroxyl 2 methyl 1 [4 (2 [hydroxyethoxy)phenyl] 1 Acetone, benzoin dimethyl ether, triphenylthionium hexafluoroantimonate or 2,2-dimethyl benzoate At least one of diethoxyacetophenone; The thermal initiator is selected from at least one of azo initiators, peroxide initiators, organotin compounds, chloroplatinic acid, (Ph3P)4Pd, [RhCl(CO)2]2, and organic bases; the azo initiator is selected from one of azobisisobutyronitrile, azobisisobutyramidine hydrochloride, and azobisisopropylimidazoline hydrochloride; the peroxide initiator is selected from one of benzoyl peroxide, tert-butyl peroxide, and methyl ethyl ketone peroxide.

5. The method for preparing a highly transparent, high-surface-hardness, and bendable coating according to claim 1, characterized in that, The surface of the nanoparticles is grafted with reactive functional groups, which are introduced by grafting with a silane coupling agent; the curable organic mixture is at least one of monofunctional olefins and polyfunctional olefins containing carbon-carbon double bonds; the reactive functional groups on the surface of the inorganic oxide nanoparticles undergo addition polymerization with the curable organic mixture.

6. The method for preparing a highly transparent, high-surface-hardness, and bendable coating according to claim 5, characterized in that, The monofunctional olefin is selected from at least one of methyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, polyethylene glycol monoacrylate, siloxane acrylate, and 4-acryloylmorpholine; the polyfunctional olefin is selected from at least one of bisphenol A acrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and epoxy acrylate.

7. The method for preparing a highly transparent, high-surface-hardness, and bendable coating according to claim 1, characterized in that, The nanoparticles are selected from one of silicon dioxide, aluminum oxide, titanium dioxide, and zirconium oxide.

8. The method for preparing a highly transparent, high-surface-hardness, and bendable coating according to claim 1, characterized in that, The thermosetting process involves curing at a temperature of 50-200℃ for 1 second to 120 minutes; the photocuring process involves curing by ultraviolet light irradiation for 1 second to 120 minutes.

9. A highly transparent, high-surface-hardness, and bendable coating, characterized in that, From bottom to top, it includes a base, a soft layer, a gradient layer, and a hard layer. During the pre-curing stage, the soft layer coating penetrates the hard layer coating to spontaneously form a gradient layer. The gradient layer is a gradient distribution structure formed by the hard layer coating components and the soft layer coating components. Along the direction away from the hard layer, the content of the hard layer coating components in the gradient layer gradually decreases while the content of the soft layer coating components gradually increases.

10. The method for preparing a highly transparent, high-surface-hardness, and bendable coating according to claim 9, characterized in that, The overall thickness of the coating is 10-300 μm, and the thickness of the gradient layer is 200 nm-1 μm.

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