A PDMS-based double-layer hydrophobic antireflective self-cleaning coating and its preparation method

Abstract

The invention provides a PDMS-based double-layer hydrophobic anti-reflection self-cleaning coating and a preparation method thereof, relating to the technical field of hydrophobic materials. The preparation method comprises the following steps: adding polydimethylsiloxane (PDMS) and a PDMS curing agent to n-hexane, mixing uniformly to obtain a PDMS sol, and dip-coating the PDMS sol on a hydroxylated substrate as a connecting layer; adding PDMS, the PDMS curing agent and dibutyltin dilaurate (DBTDL) to the n-hexane, mixing uniformly, and then adding tetraethyl orthosilicate (TEOS) / methyltrimethoxysilane (MTMS) / triethoxymethylsilane (MTES) to obtain a PDMS-SiO2 sol, and then dip-coating the PDMS-SiO2 sol on the PDMS connecting layer on the substrate to obtain a PDMS-SiO2 hydrophobic layer; and introducing a carbonization template into the PDMS-SiO2 hydrophobic layer using an external flame, and then performing an annealing treatment to obtain the PDMS-based double-layer hydrophobic anti-reflection self-cleaning coating, wherein the coating achieves the coexistence of high hydrophobicity, high durability and high light transmittance.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrophobic materials, in particular to a PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating and a preparation method thereof. Background Art

[0002] Hydrophobic surfaces are widely found in nature, including leaves of many plants, the epidermis of insects, feathers of birds, and other extended parts. In the 1970s, renowned botanist Barthelot first discovered the lotus effect during his research. This effect stems from a natural waxy, hydrophobic film on the surface of a lotus leaf. This film effectively repels water droplets, causing them to form nearly spherical droplets on the leaf surface and then flow down in streams, without wetting the leaf surface while simultaneously carrying away any dirt. This is the lotus effect. Barthelot invented self-cleaning technology based on this discovery. Existing research indicates that a super-hydrophobic surface is defined as one with a contact angle greater than 150° and a rolling angle less than 10°. A hydrophobic coating is a coating with a specialized surface structure. Its microstructure allows water droplets to form extremely high contact angles upon contact, thus achieving various desired effects.

[0003] As an advanced functional material with excellent water-repellent properties, hydrophobic materials offer effective solutions for various areas of production and life. From an application perspective, hydrophobic surfaces are particularly useful when they possess multiple functions, such as transparency, photocatalysis, and self-healing after damage. By using engineered surface structures, water droplets are formed into nearly spherical shapes, effectively removing dust, mold, and bacteria during the rolling process. Self-cleaning technology has gained widespread acceptance and is widely used in optical devices, buildings, and various industrial facilities. In the construction industry, the application of hydrophobic coatings can effectively improve the water-repellent properties of structures such as walls and roofs, extending the service life of buildings and reducing maintenance costs. In the transportation sector, the use of hydrophobic materials in automobiles, ships, and aircraft effectively prevents moisture adhesion, improving speed and safety. In the textile industry, the study of hydrophobic technology has led to the development of textile products with excellent water-repellent properties, meeting consumers' dual needs for functionality and comfort. In the electronics field, hydrophobic materials provide effective protection for electronic devices and components, preventing short circuits and damage caused by moisture, thereby extending the service life of electronic products. However, for hydrophobic materials to fully realize their hydrophobic properties, durability is crucial. In particular, in some applications, maintaining the color of the substrate is crucial, requiring the hydrophobic material to have high light transmittance. Therefore, in order to achieve both high light transmittance and durability, a coating material with self-cleaning properties and good hydrophobicity has been proposed. Summary of the Invention

[0004] In response to the problems existing in the prior art, the purpose of the present invention is to provide a PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating and a preparation method thereof. This method can not only improve the hydrophobic properties of the hydrophobic coating, but also achieve high light transmittance and durability of the coating. At the same time, the preparation process is simple, thereby solving the problem in the prior art that hydrophobic coatings are difficult to achieve coexistence of hydrophobicity, durability and high light transmittance.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, a method for preparing a PDMS-based double-layer hydrophobic antireflective self-cleaning coating comprises the following steps:

[0007] (1) preparing a PDMS sol containing a PDMS curing agent and a PDMS-SiO2 sol containing hydrophobic SiO2; and simultaneously performing a hydroxylation treatment on the substrate for standby use;

[0008] (2) dip-coating the PDMS sol on a spare substrate and drying it to obtain a PDMS connecting layer;

[0009] (3) dip-coating the PDMS-SiO2 sol on the PDMS connecting layer obtained in step (2), and drying to obtain a PDMS-SiO2 hydrophobic layer;

[0010] (4) The PDMS-SiO2 hydrophobic layer obtained in step (3) is subjected to an external flame carbonization treatment to introduce a carbonization template, and then subjected to an annealing treatment to obtain a PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating containing a PDMS connecting layer and a PDMS-SiO2 carbonization annealing layer.

[0011] Furthermore, in step (1), the concentration of the PDMS sol is 0.08 to 0.16 g / ml; and / or, in the PDMS sol, the mass ratio of PDMS to PDMS curing agent is 10:1; and / or, the hydrolysis silicon source of the hydrophobic SiO2 is selected from any one of TEOS, MTMS and MTES, further, the hydrolysis silicon source is hydrolyzed under the action of a hydrolysis catalyst, preferably, the hydrolysis catalyst is dibutyltin dilaurate, and the mass ratio of the hydrolysis catalyst to the hydrolysis silicon source is 1:4, more preferably, the concentration of TEOS in the PDMS-SiO2 sol is 0.002 to 0.02 g / mL, the concentration of MTMS in the PDMS-SiO2 sol is 0.005 to 0.05 g / mL, and the concentration of MTES in the PDMS-SiO2 sol is 0.001 to 0.025 g / mL; and / or, the hydrophobic SiO2 is nanoscale.

[0012] Furthermore, in step (1), the method for preparing the PDMS sol is as follows: adding PDMS and a PDMS curing agent to an organic solvent, stirring at 45 to 50° C. for 20 to 40 minutes to mix them evenly, to obtain the PDMS sol;

[0013] And / or, a method for preparing a PDMS-SiO2 sol is as follows: adding PDMS, a PDMS curing agent, and a hydrolysis catalyst to an organic solvent, stirring the mixture at a temperature of 40 to 45° C. for 20 to 40 minutes; then adding a hydrolysis silicon source, and stirring the mixture again at a temperature of 40 to 45° C. for 60 to 75 minutes to obtain a PDMS-SiO2 sol;

[0014] And / or, the hydroxylation treatment is performed by plasma treatment.

[0015] Furthermore, in step (2) and / or step (3), the dipping speed is 80 to 105 mm / min; and / or the drying temperature is 230 to 250° C., and the drying time is 40 to 60 min.

[0016] Furthermore, in step (4), the outer flame carbonization treatment is selected from the outer flame of a candle, a lighter or a match; and / or, the temperature of the annealing treatment is 450-500° C., and the time is 60-90 min.

[0017] In a second aspect, a PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating comprises a PDMS connecting layer and a PDMS-SiO2 carbonized annealed layer, wherein the PDMS connecting layer is located at the bottom layer and is in direct contact with the surface of a substrate, and is obtained by dip-coating the substrate with a PDMS sol containing a PDMS curing agent, wherein the substrate is a hydroxylated substrate;

[0018] The PDMS-SiO2 carbonization annealing layer is located on the top layer and connected to the PDMS connecting layer. It is obtained by dip-coating PDMS-SiO2 sol on the PDMS connecting layer, external flame carbonization, and annealing. The PDMS-SiO2 sol contains hydrophobic SiO2.

[0019] Further, the hydrolyzed silicon source of the hydrophobic SiO2 is selected from any one of TEOS, MTMS and MTES. Further, the hydrolyzed silicon source is hydrolyzed under the action of a hydrolysis catalyst. Preferably, the hydrolysis catalyst is dibutyltin dilaurate, and the mass ratio of the hydrolysis catalyst to the hydrolyzed silicon source is 1:4. More preferably, the concentration of TEOS in the PDMS-SiO2 sol is 0.002 to 0.02 g / mL, the concentration of MTMS in the PDMS-SiO2 sol is 0.005 to 0.05 g / mL, and the concentration of MTES in the PDMS-SiO2 sol is 0.001 to 0.025 g / mL; and / or, the hydrophobic SiO2 is nanoscale;

[0020] and / or, the concentration of the PDMS sol is 0.08 to 0.16 g / ml;

[0021] And / or, in the PDMS sol, the mass ratio of PDMS to PDMS curing agent is 10:1.

[0022] Furthermore, the PDMS-SiO2 carbonized annealed layer has a micro-nano rough structure.

[0023] Furthermore, when the hydrolyzed silicon source of the hydrophobic SiO2 is selected from MTES, the hydrophobic angle of the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating is 131.9°, the transmittance is 95.8%, and the pencil hardness is 3H.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention improves the pencil hardness of the coating by constructing a double-layer composite structure with a PDMS connecting layer as the bottom layer and a PDMS-SiO2 carbonized annealed layer as the top layer, thereby obtaining a highly durable characteristic. At the same time, the PDMS-SiO2 carbonized annealed layer is prepared using a raw material that can generate hydrophobic SiO2 in situ. Even after being carbonized to black and annealed to become transparent again, the light transmittance of the double-layer coating with the PDMS-SiO2 carbonized annealed layer is significantly higher than that of the PDMS carbonized annealed coating and the PDMS coating, reaching about 95%. In the specific preparation, a pull-up and immersion dipping method can be used in conjunction with carbonization annealing treatment to achieve the coexistence of high hydrophobicity, high durability and high light transmittance of the hydrophobic coating, and the preparation process is simple. The method of the present invention solves the problem in the prior art that it is difficult for hydrophobic coatings to achieve the coexistence of hydrophobicity, durability and high light transmittance.

[0026] (2) The present invention uses MTMS / MTES to prepare nano-SiO2. The hydrophobic methyl groups of MTMS / MTES can be used to obtain nano-SiO2 modified with in-situ hydrophobic methyl groups, thereby having better hydrophobicity. In particular, when the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating of the present invention is prepared by adding MTES to hydrolyze the nano-SiO2, the overall performance of the coating is relatively better, with a hydrophobic angle of 131.9°, a transmittance of 95.8%, and a pencil hardness of 3H.

[0027] (3) The present invention achieves high light transmittance of the composite coating through TEOS / MTMS / MTES because TEOS / MTMS / MTES itself has an anti-reflection effect, which provides a new direction for designing hydrophobic anti-reflection self-cleaning coatings.

[0028] (4) The hydrophobic, anti-reflective and self-cleaning coating of the present invention is suitable for solid surfaces such as glass and metal, and can be used for self-cleaning of devices such as photovoltaics, solar energy, ships, and wind turbine blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 Figure 1 is a graph of the hydrophobic angles of the single-layer coatings and double-layer coatings obtained in Examples 1-3 of the present invention and Comparative Example 1, wherein ad is the hydrophobic angle of a single-layer PDMS coating, and a double-layer PDMS / PDMS-TEOS coating, PDMS / PDMS-MTMS coating, and PDMS / PDMS-MTES coating, respectively; eh is the hydrophobic angle of a single-layer PDMS carbonized coating, and a double-layer PDMS / PDMS-TEOS carbonized coating, PDMS / PDMS-MTMS carbonized coating, and PDMS / PDMS-MTES carbonized coating, respectively; and il is the hydrophobic angle of a single-layer PDMS carbonized annealed coating, and a double-layer PDMS / PDMS-TEOS carbonized annealed coating, PDMS / PDMS-MTMS carbonized annealed coating, and PDMS / PDMS-MTES carbonized annealed coating, respectively;

[0031] Figure 2These are the transmittance graphs of the single-layer coatings and double-layer coatings obtained in Examples 1-3 of the present invention and Comparative Example 1, where ad are coatings after carbonization annealing, a is a PDMS carbonization annealing coating, b is a PDMS / PDMS-TEOS carbonization annealing coating, c is a PDMS / PDMS-MTMS carbonization annealing coating, d is a PDMS / PDMS-MTES carbonization annealing coating, and e is a PDMS coating. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. The process parameters for which specific conditions are not specified in the following examples are generally in accordance with conventional conditions.

[0033] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0034] Throughout this disclosure, unless otherwise specified and / or explained, all numerical values ​​referring to content are by mass, volume, or concentration. Process parameters in the following examples, where specific conditions are not specified, generally follow conventional conditions. The raw materials described in the following examples were all obtained from publicly available commercial sources.

[0035] According to a first aspect of the present invention, the present invention provides a method for preparing a PDMS-based double-layer hydrophobic antireflective self-cleaning coating, comprising the following steps:

[0036] (1) preparing a PDMS sol containing a PDMS curing agent and a PDMS-SiO2 sol containing hydrophobic SiO2; and simultaneously performing a hydroxylation treatment on the substrate for standby use;

[0037] (2) dip-coating the PDMS sol on a spare substrate and drying it to obtain a PDMS connecting layer;

[0038] (3) dip-coating the PDMS-SiO2 sol on the PDMS connecting layer obtained in step (2), and drying to obtain a PDMS-SiO2 hydrophobic layer;

[0039] (4) The PDMS-SiO2 hydrophobic layer obtained in step (3) is subjected to an external flame carbonization treatment to introduce a carbonization template, and then subjected to an annealing treatment to obtain a PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating containing a PDMS connecting layer and a PDMS-SiO2 carbonization annealing layer.

[0040] The PDMS (polydimethylsiloxane)-based double-layer hydrophobic, anti-reflective, self-cleaning coating prepared by the method of the present invention exhibits superior durability, light transmittance, and hydrophobicity compared to single-layer PDMS coatings. After extensive research, the inventors discovered that although carbonization annealing treatment increases the hydrophobicity and light transmittance of single-layer PDMS coatings, with the light transmittance increasing to approximately 92%, the pencil hardness of the carbonized annealed PDMS single-layer coating is poor, only B, failing to achieve a good balance between durability and light transmittance, and its light transmittance needs to be improved. However, constructing a double-layer composite structure with a PDMS connecting layer as the bottom layer and a PDMS-SiO2 carbonized annealed layer as the top layer can improve the pencil hardness of the carbonized annealed PDMS coating, thereby achieving high durability. At the same time, the PDMS-SiO2 carbonization annealing layer is prepared using raw materials that can generate hydrophobic SiO2 in situ, which not only improves the hydrophobicity of the PDMS coating, but also significantly improves the light transmittance of the PDMS coating. Even after carbonization and blackening, annealing and then becoming transparent, the light transmittance of the double-layer coating can still reach about 95%. During the specific preparation, a pull-up and dipping dip coating method can be used in conjunction with carbonization annealing treatment to achieve the coexistence of high hydrophobicity, high durability and high light transmittance of the hydrophobic coating, and the preparation process is simple. The method of the present invention solves the problem in the prior art that it is difficult for hydrophobic coatings to achieve the coexistence of hydrophobicity, durability and high light transmittance.

[0041] The technical mechanism of the present invention is as follows: a coating sol, namely a PDMS sol and a PDMS-SiO2 sol, is sequentially attached to a hydroxylated substrate such as a plasma-treated glass slide by a dip-coating method to construct a double-layer composite structure to achieve a highly durable coating. The present invention provides hydrophobicity derived from two aspects: first, the micro-nanostructure provided by nano-SiO2 obtained by hydrolysis of a hydrolyzed silicon source, such as tetraethyl orthosilicate (TEOS) / methyltrimethoxysilane (MTMS) / triethoxymethylsilane (MTES); and second, a rough structure provided by the introduction of a carbonized template to achieve hydrophobicity. Although the carbonized template increases hydrophobicity, the introduction of the carbonized template causes the coating to turn black. Therefore, an annealing treatment is performed to allow the blackened coating to volatilize through the high-temperature generation of CO2, thereby restoring transparency.

[0042] In particular, when the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating of the present invention is prepared, when nano-SiO2 is prepared by adding MTES hydrolysis, its overall performance results are relatively better, with a hydrophobic angle of 131.9°, a transmittance of 95.8%, and a pencil hardness of 3H.

[0043] As an optional embodiment of the preparation method of the present invention, in step (1), the concentration of the PDMS sol is 0.08-0.16 g / ml (the concentration of the PDMS sol refers to the concentration of PDMS therein, which can be typically but not limited to 0.09 g / ml, 0.10 g / ml, 0.11 g / ml, 0.12 g / ml, 0.13 g / ml, 0.14 g / ml, 0.15 g / ml); and / or, in the PDMS sol, the mass ratio of PDMS to PDMS curing agent is 10:1; and / or, the hydrolyzable silicon source of the hydrophobic SiO2 is selected from any one of TEOS, MTMS and MTES, further, the hydrolyzable silicon source is hydrolyzed under the action of a hydrolysis catalyst, preferably, the hydrolysis catalyst is dibutyltin dilaurate (DBTDL), and the mass ratio of the hydrolysis catalyst to the hydrolyzable silicon source is 1:4, more preferably, the PDMS-SiO The concentration of TEOS in the sol is 0.002-0.02 g / mL (e.g., 0.005 g / ml, 0.010 g / ml, 0.015 g / ml, 0.018 g / ml), and the concentration of MTMS in the PDMS-SiO2 sol is 0.005-0.05 g / mL (e.g., 0.01 g / ml, 0.015 g / ml, 0.02 g / ml, 0.025 g / ml, 0.03 g / ml, 0.06 g / ml, 0.07 g / ml, 0.08 g / ml, 0.10 g / ml, 0.15 g / ml, 0.09 g / ml, 0.11 g / ml, 0.12 g / ml, 0.13 g / ml, 0.14 g / ml, 0.16 g / ml, 0.17 g / ml, 0.18 g / ml, 0.19 g / ml, 0.20 g / ml, 0.21 g / ml, 0.22 g / ml, 0.23 g / ml, 0.24 g / ml, 0.25 g / ml, 0.26 g / ml, 0.27 g / ml, 0.28 g / ml, 0.29 g / ml, 0.30 g / ml, 0.31 g / ml, 0.32 g / ml, .035g / ml, 0.04g / ml, 0.045g / ml), the concentration of MTES in the PDMS-SiO2 sol is 0.001-0.025g / mL (such as 0.005g / mL, 0.010g / mL, 0.015g / mL, 0.018g / ml, 0.020g / ml, 0.022g / ml, 0.024g / ml); and / or the hydrophobic SiO2 is nanoscale.

[0044] The above technical scheme realizes the high light transmittance characteristic of composite coating by TEOS / MTMS / MTES, and is because TEOS / MTMS / MTES itself has antireflection effect, and provides new direction for designing hydrophobic antireflection self-cleaning coating. In addition, no matter hydrolysis silicon source is TEOS or MTMS or MTES, SiO2 in coating is in-situ generated, is nano-scale, and all has hydrophobicity. And further, select to use MTMS / MTES to prepare nano-SiO2, its hydrophobicity is better, because MTMS / MTES has hydrophobic methyl group, thereby makes the nano-SiO2 prepared, has methyl group of in-situ hydrophobic modification, and compared with the nano-SiO2 prepared by TEOS, has better hydrophobicity.

[0045] As an optional embodiment of the preparation method of the present invention, in step (1), the method for preparing the PDMS sol is as follows: PDMS and a PDMS curing agent are added to an organic solvent, and stirred at 45 to 50° C. (e.g., 46° C., 47° C., 48° C., 49° C.) for 20 to 40 minutes (e.g., 25 minutes, 30 minutes, 35 minutes) to mix them uniformly, thereby obtaining the PDMS sol;

[0046] And / or, the method for preparing PDMS-SiO2 sol is as follows: PDMS, PDMS curing agent and hydrolysis catalyst are added to an organic solvent and stirred at a temperature of 40 to 45°C (e.g., 41°C, 42°C, 43°C, 44°C) for 20 to 40 minutes (e.g., 25 minutes, 30 minutes, 35 minutes); then a hydrolysis silicon source is added and stirred again at a temperature of 40 to 45°C (e.g., 41°C, 42°C, 43°C, 44°C) for 60 to 75 minutes (e.g., 65 minutes, 70 minutes) to obtain a PDMS-SiO2 sol;

[0047] And / or, the hydroxylation treatment is performed by plasma treatment.

[0048] In the above technical solution, the control of the stirring temperature and reaction time is to ensure sufficient mixing, especially during the hydrolysis reaction, to fully generate SiO2. However, the temperature and time do not have much effect. The hydrolysis time is long at a low temperature, so it can also be carried out at room temperature. It’s just that the hydrolysis at room temperature is slightly slow, affecting the preparation efficiency, while the hydrolysis at a high temperature will be too fast, which may cause the nano-SiO2 to clump and become rough.

[0049] The purpose of hydroxylation of the substrate is to allow the hydroxyl groups (-OH) on the substrate surface to react with the silanol groups (Si-OH) in the coating sol to form Si-O-Si, thereby improving the adhesion between the substrate and the coating. Hydroxylation can also be performed by methods other than plasma treatment, as long as the substrate surface is hydroxylated.

[0050] In addition, the organic solvent used in the preparation of the sol of the present invention can be optional, as long as it can dissolve the relevant raw materials and evaporate when the coating is dried, such as n-hexane and toluene.

[0051] As an optional embodiment of the preparation method of the present invention, in step (2) and / or step (3), the dipping speed is 80-105 mm / min (for example, 82 mm / min, 84 mm / min, 86 mm / min, 88 mm / min, 90 mm / min, 92 mm / min, 94 mm / min, 96 mm / min, 98 mm / min, 100 mm / min, 102 mm / min, 104 mm / min); and / or the drying temperature is 230-250° C. (for example, 235° C., 240° C., 245° C.), and the drying time is 40-60 min (for example, 45 min, 50 min, 55 min).

[0052] In the above technical solution, a dipping method of pulling and dipping can be used. The specific operation can be as follows: during dipping, the substrate, such as a glass sheet, is completely immersed in the sol vertically, the dipping speed is 80-105 mm / min, and the holding time is 25-32 s (for example, 27 s, 29 s, 30 s), and then the glass sheet is pulled out of the sol at a speed of 142-155 mm / min (for example, 145 mm / min, 148 mm / min, 150 mm / min, 152 mm / min), and repeated three times, with an interval time of 56-75 s each time (for example, 58 s, 60 s, 62 s, 64 s, 66 s, 68 s, 70 s, 72 s).

[0053] In the present invention, there is no specific requirement for the equipment required for the processes such as dipping, drying, and annealing, as long as the relevant purposes such as dipping, drying, and annealing can be achieved. For example, drying and annealing can be performed using a muffle furnace in the prior art.

[0054] As an optional embodiment of the preparation method of the present invention, in the step (4), the outer flame carbonization treatment is selected from the outer flame of a candle, a lighter or a match; and / or the temperature of the annealing treatment is 450-500°C (for example, 455°C, 460°C, 465°C, 470°C, 475°C, 480°C, 485°C, 490°C, 495°C), and the time is 60-90 min (for example, 65 min, 70 min, 75 min, 80 min, 85 min).

[0055] The flame includes an outer flame, an inner flame and a flame core. The method of the present invention uses the outer flame in full contact with the air to carbonize the PDMS in the coating to obtain a rough structure and increase the hydrophobicity. Among them, it is preferred to use a candle for outer flame carbonization because the candle is easy to fix and can provide a stable outer flame for a long time, ensuring that the coating is in good contact with the outer flame during carbonization. The specific operation can be as follows: Use tweezers to clamp the substrate, the coating faces the candle flame, and then along the length direction of the substrate (i.e., the direction parallel to the coating), from one end to the other, horizontally pass through the top of the candle flame, i.e., the candle outer flame, to carbonize the PDMS. The carbonization temperature is the temperature of the candle outer flame. The surface of the coating turns completely black after being burned by the outer flame from one end to the other, indicating that the carbonized template has been introduced. The coating with the carbonized template introduced is placed in a muffle furnace for annealing treatment. The annealing temperature is 450-500℃ and the time is 60-90min. The carbonized template generates carbon dioxide (CO2) at high temperature and evaporates, and finally a transparent coating is obtained. Although the volatilization of carbon dioxide during annealing will affect the roughness of the coating to a certain extent, the roughness is still increased compared to the coating formed by simple dip-coating and drying before carbonization annealing. In other words, the hydrophobicity of the coating annealed after carbonization is still better than that of the coating formed by simple dip-coating and drying. During annealing, the temperature and time must be controlled within the aforementioned range. This can avoid the annealing temperature being too low within the same annealing time, which will leave a carbonized template and fail to meet the required light transmittance, and also avoid the annealing temperature being too high, which will damage the coating and fail to achieve the purpose of improving durability.

[0056] According to a second aspect of the present invention, there is provided a PDMS-based double-layer hydrophobic antireflective self-cleaning coating, comprising a PDMS connecting layer and a PDMS-SiO2 carbonized annealed layer, wherein the PDMS connecting layer is located at the bottom layer and is in direct contact with the surface of the substrate, and is obtained by dip-coating the substrate with a PDMS sol containing a PDMS curing agent, wherein the substrate is a hydroxylated substrate;

[0057] The PDMS-SiO2 carbonization annealing layer is located on the top layer and connected to the PDMS connecting layer. It is obtained by dip-coating PDMS-SiO2 sol on the PDMS connecting layer, external flame carbonization, and annealing. The PDMS-SiO2 sol contains hydrophobic SiO2.

[0058] The PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating described in the second aspect of the present invention is prepared by the method described in the first aspect.

[0059] As an optional embodiment of the PDMS-based double-layer hydrophobic antireflective self-cleaning coating of the present invention, the hydrolyzed silicon source of the hydrophobic SiO2 is selected from any one of TEOS, MTMS and MTES. Further, the hydrolyzed silicon source is hydrolyzed under the action of a hydrolysis catalyst. Preferably, the hydrolysis catalyst is dibutyltin dilaurate, and the mass ratio of the hydrolysis catalyst to the hydrolysis silicon source is 1:4. More preferably, the concentration of TEOS in the PDMS-SiO2 sol is 0.002 to 0.02 g / mL (such as 0.005 g / mL, 0.010 g / mL, 0.015 g / mL, 0.018 g / ml), and the PDMS-SiO2 sol is 0.002 to 0.02 g / mL (such as 0.005 g / mL, 0.010 g / mL, 0.015 g / mL, 0.018 g / ml). The concentration of MTMS is 0.005-0.05 g / mL (e.g., 0.01 g / ml, 0.015 g / ml, 0.02 g / ml, 0.025 g / ml, 0.03 g / ml, 0.035 g / ml, 0.04 g / ml, 0.045 g / ml), and the concentration of MTES in the PDMS-SiO2 sol is 0.001-0.025 g / mL (e.g., 0.005 g / mL, 0.010 g / mL, 0.015 g / mL, 0.018 g / ml, 0.020 g / ml, 0.022 g / ml, 0.024 g / ml); and / or, the hydrophobic SiO2 is nanoscale;

[0060] and / or, the concentration of the PDMS sol is 0.08 to 0.16 g / ml (e.g., 0.10 g / mL, 0.12 g / mL, 0.14 g / mL);

[0061] And / or, in the PDMS sol, the mass ratio of PDMS to PDMS curing agent is 10:1.

[0062] As an optional embodiment of the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating of the present invention, the PDMS-SiO2 carbonized annealed layer has a micro-nano rough structure.

[0063] As an optional embodiment of the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating of the present invention, when the hydrolyzed silicon source of the hydrophobic SiO2 is selected from MTES, the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating has a hydrophobic angle of 131.9°, a transmittance of 95.8%, and a pencil hardness of 3H.

[0064] The following describes the invention with reference to specific embodiments and comparative examples.

[0065] The sources of the reagents used in the experiments of the present invention are: polydimethylsiloxane (PDMS) (Dow Corning, specification DC184), PDMS curing agent (Dow Corning, specification SYLGARD184), dibutyltin dilaurate (Shanghai Maclean Biochemical Technology Co., Ltd., specification analytical grade), MTES and MTMS (Shanghai Maclean Biochemical Technology Co., Ltd., specification analytical grade), TEOS (Tianjin Damao Chemical Reagent Factory, specification analytical grade), and n-hexane (Tianjin Best Chemical Co., Ltd., specification analytical grade).

[0066] Example 1

[0067] This embodiment provides a PDMS-based double-layer super-hydrophobic self-cleaning coating and a preparation method thereof, the preparation method comprising the following steps:

[0068] Step 1: Slowly add 10 g of polydimethylsiloxane (PDMS) and 1 g of PDMS curing agent into 100 mL of n-hexane, place in a magnetic stirrer at 45-50° C. and stir for 30 min to obtain a PDMS sol.

[0069] Step 2: Slowly add 10g PDMS, 1g PDMS curing agent, and 0.5g dibutyltin dilaurate (DBTDL) to 100mL n-hexane, and stir with a magnetic stirrer for 30min at a temperature of 40-45°C; then add 2g tetraethyl orthosilicate (TEOS), and stir with a magnetic stirrer at a temperature of 40-45°C for 60min to obtain PDMS-SiO2 sol (PDMS-TEOS sol), where SiO2 is hydrophobic SiO2, nanoscale, and obtained by hydrolysis of TEOS.

[0070] Step 3: Use the dip coating method to dip-coat the PDMS sol on the plasma-treated glass slide. During dip coating, the glass slide is completely immersed in the sol. The dipping speed is 90 mm / min and the holding time is 30 seconds. Then the glass slide is pulled out of the sol at a speed of 150 mm / min. Repeat three times, with an interval of 1 minute each time. After the dip coating is completed, the glass slide is placed in a muffle furnace and baked at 230-250°C for 40-60 minutes to obtain a PDMS coating (PDMS connecting layer).

[0071] Step 4: Use the dip coating method to dip-coat the PDMS-SiO2 sol on the PDMS connecting layer. The dip coating method is the same as step 3. After the dip coating is completed, place the glass sheet in a muffle furnace and bake it at 230-250°C for 40-60 minutes to construct a double-layer coating structure of the PDMS connecting layer and the PDMS-SiO2 hydrophobic layer, and then obtain a PDMS-based double-layer coating (PDMS / PDMS-TEOS coating).

[0072] Step 5: Carry out the experiment of introducing carbonization template. Use tweezers to clamp the glass slide, and pass the PDMS-SiO2 hydrophobic layer on the coating surface horizontally through the top of the candle until it turns completely black, and the carbonization template is successfully introduced to obtain a coating containing a PDMS connecting layer and a PDMS-SiO2 carbonization layer (PDMS / PDMS-TEOS carbonization coating); then place the glass slide with the carbonization template introduced in a muffle furnace for annealing treatment at an annealing temperature of 450-500°C for 60-90 minutes, so that the carbonization template generates carbon dioxide (CO2) at high temperature and evaporates, and finally obtains a PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating (PDMS / PDMS-TEOS carbonization annealing coating) containing a PDMS connecting layer and a PDMS-SiO2 carbonization annealing layer.

[0073] Example 2

[0074] The difference from Example 1 is that the hydrolyzed silicon source for obtaining nano-scale hydrophobic SiO2 by hydrolysis in step 2 is methyltrimethoxysilane (MTMS), and the other steps are the same as in Example 1.

[0075] Step 1: Slowly add 10 g of polydimethylsiloxane (PDMS) and 1 g of PDMS curing agent into 100 mL of n-hexane, place in a magnetic stirrer at 45-50° C. and stir for 30 min to obtain a PDMS sol.

[0076] Step 2: Slowly add 10g PDMS, 1g PDMS curing agent, and 0.5g dibutyltin dilaurate (DBTDL) to 100mL n-hexane, and stir with a magnetic stirrer for 30min at a temperature of 40-45°C; then add 2g methyltrimethoxysilane (MTMS), and stir with a magnetic stirrer at a temperature of 40-45°C for 60min to obtain PDMS-SiO2 sol (PDMS-MTMS sol), where SiO2 is hydrophobic SiO2, nanoscale, and obtained by hydrolysis of MTMS.

[0077] Step 3: Use the dip coating method to dip-coat the PDMS sol on the plasma-treated glass slide. During dip coating, the glass slide is completely immersed in the sol. The dipping speed is 90 mm / min and the holding time is 30 seconds. Then the glass slide is pulled out of the sol at a speed of 150 mm / min. Repeat three times, with an interval of 1 minute each time. After the dip coating is completed, the glass slide is placed in a muffle furnace and baked at 230-250°C for 40-60 minutes to obtain a PDMS coating (PDMS connecting layer).

[0078] Step 4: Use the dip coating method to dip-coat the PDMS-SiO2 sol on the PDMS connecting layer. The dip coating method is the same as step 3. After the dip coating is completed, place the glass sheet in a muffle furnace and bake it at 230-250°C for 40-60 minutes to construct a double-layer coating structure of the PDMS connecting layer and the PDMS-SiO2 hydrophobic layer, and then obtain a PDMS-based double-layer coating (PDMS / PDMS-MTMS coating).

[0079] Step 5: Carry out the experiment of introducing carbonization template. Use tweezers to clamp the glass slide, and pass the PDMS-SiO2 hydrophobic layer on the coating surface horizontally through the top of the candle until it turns completely black, and the carbonization template is successfully introduced to obtain a coating containing a PDMS connecting layer and a PDMS-SiO2 carbonization layer (PDMS / PDMS-MTMS carbonization coating); then place the glass slide with the carbonization template introduced in a muffle furnace for annealing treatment at an annealing temperature of 450-500°C for 60-90 minutes, so that the carbonization template generates carbon dioxide (CO2) at high temperature and evaporates, and finally obtains a PDMS-based double-layer hydrophobic anti-reflection self-cleaning coating (PDMS / PDMS-MTMS carbonization annealing coating) containing a PDMS connecting layer and a PDMS-SiO2 carbonization annealing layer.

[0080] Example 3

[0081] The difference from Example 1 is that the hydrolyzed silicon source for obtaining nano-scale hydrophobic SiO2 by hydrolysis in Step 2 is triethoxymethylsilane (MTES), and the other steps are the same as in Example 1.

[0082] Step 1: Slowly add 10 g of polydimethylsiloxane (PDMS) and 1 g of PDMS curing agent into 100 mL of n-hexane, place in a magnetic stirrer at 45-50° C. and stir for 30 min to obtain a PDMS sol.

[0083] Step 2: Slowly add 10g PDMS, 1g PDMS curing agent, and 0.5g dibutyltin dilaurate (DBTDL) to 100mL n-hexane, and stir with a magnetic stirrer for 30min at a temperature of 40-45°C; then add 2g triethoxymethylsilane (MTES), and stir with a magnetic stirrer at a temperature of 40-45°C for 60min to obtain PDMS-SiO2 sol (PDMS-MTES sol), where SiO2 is hydrophobic SiO2, nanoscale, and obtained by hydrolysis of MTES.

[0084] Step 3: Use the dip coating method to dip-coat the PDMS sol on the plasma-treated glass slide. During dip coating, the glass slide is completely immersed in the sol. The dipping speed is 90 mm / min and the holding time is 30 seconds. Then the glass slide is pulled out of the sol at a speed of 150 mm / min. Repeat three times, with an interval of 1 minute each time. After the dip coating is completed, the glass slide is placed in a muffle furnace and baked at 230-250°C for 40-60 minutes to obtain a PDMS coating (PDMS connecting layer).

[0085] Step 4: Use the dip coating method to dip-coat the PDMS-SiO2 sol on the PDMS connecting layer. The dip coating method is the same as step 3. After the dip coating is completed, place the glass sheet in a muffle furnace and bake it at 230-250°C for 40-60 minutes to construct a double-layer coating structure of the PDMS connecting layer and the PDMS-SiO2 hydrophobic layer, and then obtain a PDMS-based double-layer coating (PDMS / PDMS-MTES coating).

[0086] Step 5: Carry out the experiment of introducing the carbonization template. Use tweezers to clamp the glass slide, and pass the PDMS-SiO2 hydrophobic layer on the coating surface horizontally through the top of the candle until it turns completely black, and the carbonization template is successfully introduced to obtain a coating containing a PDMS connecting layer and a PDMS-SiO2 carbonization layer (PDMS / PDMS-MTES carbonization coating); then place the glass slide with the carbonization template introduced in a muffle furnace for annealing treatment at an annealing temperature of 450-500°C for 60-90 minutes, so that the carbonization template generates carbon dioxide (CO2) at high temperature and evaporates, and finally obtains a PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating (PDMS / PDMS-MTES carbonization annealing coating) containing a PDMS connecting layer and a PDMS-SiO2 carbonization annealing layer.

[0087] Comparative Example 1

[0088] The difference from Example 1 is that there are no steps 2 and 4. The other steps are the same as Example 1; specifically, they are as follows:

[0089] Step 1: Slowly add 10 g of polydimethylsiloxane (PDMS) and 1 g of PDMS curing agent into 100 mL of n-hexane, place in a magnetic stirrer at 45-50° C. and stir for 30 min to obtain a PDMS sol.

[0090] Step 2: Use the dip coating method to dip-coat the PDMS sol on the plasma-treated glass slide. During dip coating, the glass slide is completely immersed in the sol. The dipping speed is 90 mm / min and the holding time is 30 seconds. Then the glass slide is pulled out of the sol at a speed of 150 mm / min. Repeat three times, with an interval of 1 minute each time. After the dip coating is completed, the glass slide is placed in a muffle furnace and baked at 230-250°C for 40-60 minutes to obtain a PDMS coating (PDMS connecting layer).

[0091] Step 3: Carry out the experiment of introducing carbonization template. Use tweezers to clamp the glass sheet and pass the coating surface horizontally through the top of the candle until it turns completely black, and the carbonization template is successfully introduced to obtain the PDMS carbonization coating; then place the glass sheet with the carbonization template introduced in a muffle furnace for annealing treatment. The annealing temperature is 450-500℃ and the time is 60-90min, so that the carbonization template generates carbon dioxide (CO2) at high temperature and evaporates, and finally a transparent PDMS hydrophobic self-cleaning coating (PDMS carbonization annealing coating) is obtained.

[0092] Performance testing and result analysis

[0093] The PDMS coatings, PDMS / PDMS-TEOS coatings, PDMS / PDMS-MTMS coatings, PDMS / PDMS-MTES coatings, PDMS / PDMS-TEOS carbonized coatings, PDMS / PDMS-MTMS carbonized coatings, PDMS / PDMS-MTES carbonized coatings, PDMS / PDMS-TEOS carbonized annealed coatings, PDMS / PDMS-MTMS carbonized annealed coatings, PDMS / PDMS-MTES carbonized annealed coatings obtained in Examples 1 to 3, and the PDMS carbonized coatings and PDMS carbonized annealed coatings obtained in Comparative Example 1 were subjected to at least one of the following tests, specifically as follows:

[0094] (1) Self-cleaning performance test analysis

[0095] Place all glass slides (glass slides) on the same plane with the coating or test surface facing up. Then use a sieve to completely cover all test surfaces with artificial dust. Sieve the dust horizontally and evenly so that the dust is evenly sprinkled on the test surface of the glass slide. Drip water from one end of the test surface to perform a self-cleaning test on the coating.

[0096] Test results show that the coated glass surfaces repel dust significantly better than blank glass. When water droplets roll across the coated glass, they successfully remove dust from the surface, keeping the glass clean. This demonstrates the excellent self-cleaning capabilities of these coating samples. Further observation reveals that as the water droplets roll down, they form tiny vortices on the coating surface. These vortices effectively carry away impurities from the coating surface along with the water droplets. This demonstrates that these coatings are hydrophobic and self-cleaning, enabling the glass to achieve its self-cleaning function once attached to the surface.

[0097] (2) Hydrophobic angle test analysis

[0098] To further investigate the coating's hydrophobicity, the present invention employed a contact angle meter to measure the contact angle of water droplets on coatings with varying raw material ratios. Specifically, a drop of deionized water was dripped onto the sample coating surface using a syringe. The hydrophobicity of the sample coating was characterized by observing and analyzing the contact angle between the water droplet and the coating surface.

[0099] like Figure 1As shown in Figure 2, ad are the hydrophobic angles of the single-layer PDMS coating formed by dip-coating PDMS, PDMS-TEOS, PDMS-MTMS, and PDMS-MTES sol, as well as the double-layer PDMS / PDMS-TEOS coating, PDMS / PDMS-MTMS coating, and PDMS / PDMS-MTES coating, which are 114.7°, 117.2°, 118.5°, and 119.5°, respectively. Compared with the single-layer PDMS coating, the hydrophobic angles of the double-layer coatings are increased, which shows that the hydrophobic angles of the double-layer coatings are all hydrophobic. The nano-SiO2 obtained by decomposition is provided; eh is a single-layer PDMS carbonized coating formed by dip-coating PDMS, PDMS-TEOS, PDMS-MTMS, PDMS-MTES sol and introducing a carbonized template, as well as a double-layer PDMS / PDMS-TEOS carbonized coating, PDMS / PDMS-MTMS carbonized coating and PDMS / PDMS-MTES carbonized coating. Compared with the hydrophobic angle range of 114.7°-119.5° of the coating obtained by simple dip coating and drying, the hydrophobic angles reach 158.8°, 157.6°, and 157.6°, respectively. 160.8°, 161.2°, which shows that the carbonization template is successfully introduced, and the carbonization template has a rough structure. The carbonization template makes the coating have a rough structure to achieve a superhydrophobic effect; il is a single-layer PDMS carbonized annealed coating formed by dip-coating PDMS, PDMS-TEOS, PDMS-MTMS, PDMS-MTES sol and carbonization annealing, as well as a double-layer PDMS / PDMS-TEOS carbonized annealed coating, PDMS / PDMS-MTMS carbonized annealed coating and PDMS / PDMS-MTES carbonized annealed coating. The hydrophobic angles of the carbonized template are 133.2°, 130.5°, 120.7°, and 131.9°, respectively. Although the carbonized template generates CO2 through high-temperature baking and volatilization, which restores transparency, the hydrophobic angle is reduced compared to when the carbonized template is introduced, but increased compared to when it is dip-coated. This indicates that the volatilization of carbon dioxide during annealing will affect the roughness of the coating to a certain extent. However, compared with the coating formed by simple dip-coating and drying before carbonization annealing, the roughness is still increased. That is, the hydrophobicity of the coating annealed after carbonization is still better than that of the coating formed by simple dip-coating and drying. In particular, the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating of the present invention has better hydrophobicity than the single-layer PDMS coating.

[0100] The above hydrophobic angle test results also prove that (1) in the self-cleaning performance test, each coating is indeed hydrophobic and can self-clean, but the self-cleaning performance of the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating of the present invention is better than that of the PDMS coating.

[0101] (3) Transmittance test analysis

[0102] This test used an ultraviolet spectrophotometer to measure the transmittance of a series of hydrophobic coatings with different raw material ratios at room temperature. The wavelength range used in the test was 300-1100nm, and the instrument was calibrated by running dry.

[0103] Figure 2 Figures show the transmittance of a bare glass slide, a PDMS coating attached to the slide, a single-layer carbonized annealed PDMS coating, a double-layer carbonized annealed PDMS / PDMS-TEOS coating, a double-layer carbonized annealed PDMS / PDMS-MTMS coating, and a double-layer carbonized annealed PDMS / PDMS-MTES coating. As shown in the figure, the maximum transmittance in the visible light range is as follows: bare glass has a transmittance of 91%; (a) a single-layer carbonized annealed PDMS coating has a transmittance of 92.6%; (b) a double-layer carbonized annealed PDMS / PDMS-TEOS coating has a transmittance of 94.7%; (c) a double-layer carbonized annealed PDMS / PDMS-MTMS coating has a transmittance of 96%; (d) a double-layer carbonized annealed PDMS / PDMS-MTES coating has a transmittance of 95.8%; and (e) a PDMS coating has a transmittance of 89%. Compared to a bare glass slide, the transmittance of the PDMS coating formed by coating with PDMS sol decreased. Although it increased somewhat after carbonization and annealing, it was still less transparent than a glass slide dipped in PDMS sol and then PDMS-SiO2 sol and then carbonized and annealed. This indicates that the TEOS, MTMS, and MTES added to the double-layer structure have an anti-reflective effect, achieving the coating's high light transmittance. Furthermore, the light transmittance of the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating of the present invention is far superior to that of the PDMS coating.

[0104] (4) Pencil hardness test analysis

[0105] According to the standard test method for coating properties (GBT6739), the hardness of a hydrophobic coating is evaluated by whether a pencil scratch can penetrate the coating. The maximum pencil hardness the coating can withstand (classified from soft to hard, 6B-6H) is measured. The different composite coatings tested had different pencil hardness values. The single-layer PDMS carbonized annealed coating had a pencil hardness of B, while the double-layer PDMS / PDMS-TEOS carbonized annealed coating reached a pencil hardness of 3H, the PDMS / PDMS-MTMS carbonized annealed coating reached a pencil hardness of 4H, and the PDMS / PDMS-MTES carbonized annealed coating reached a pencil hardness of 3H. This indicates that the double-layer composite structure increases the pencil hardness of the coating, and therefore, the durability can be improved by constructing a double-layer structure.

[0106] In summary, the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating prepared by the method of the present invention simultaneously possesses high hydrophobicity, high durability, and high light transmittance, resolving the problem of hydrophobic coatings in the prior art that it is difficult to achieve the coexistence of hydrophobicity, durability, and high light transmittance. Furthermore, when the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating of the present invention is prepared by adding MTES to produce nano-SiO2 by hydrolysis, the overall performance of the coating is relatively better, with a hydrophobic angle of 131.9°, a light transmittance of 95.8%, and a pencil hardness of 3H.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a PDMS-based double-layer hydrophobic antireflective self-cleaning coating, characterized in that: The following steps are involved: (1) Prepare a PDMS sol containing a PDMS curing agent and a PDMS-SiO2 sol containing hydrophobic SiO2; and simultaneously perform a hydroxylation treatment on the substrate for later use; The method for preparing the PDMS-SiO2 sol is as follows: PDMS, a PDMS curing agent, and a hydrolysis catalyst are added to an organic solvent and stirred at a temperature of 40-45°C for 20-40 minutes; then a hydrolysis silicon source is added and stirred again at a temperature of 40-45°C for 60-75 minutes to obtain the PDMS-SiO2 sol; The hydrophobic SiO2 is nanometer-sized; (2) dip-coating the PDMS sol on a spare substrate and drying it to obtain a PDMS connecting layer; (3) dip-coating the PDMS-SiO2 sol on the PDMS connecting layer obtained in step (2), and drying to obtain a PDMS-SiO2 hydrophobic layer; (4) The PDMS-SiO2 hydrophobic layer obtained in step (3) is subjected to an external flame carbonization treatment to introduce a carbonization template, and then subjected to an annealing treatment to obtain a PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating containing a PDMS connecting layer and a PDMS-SiO2 carbonization annealing layer.

2. The method for preparing a PDMS-based double-layer hydrophobic antireflective self-cleaning coating according to claim 1, characterized in that: In step (1), the concentration of the PDMS sol is 0.08~0.16g / ml; and / or, in the PDMS sol, the mass ratio of PDMS to PDMS curing agent is 10:1; and / or, the hydrolysis silicon source of the hydrophobic SiO2 is selected from any one of TEOS, MTMS and MTES, the hydrolysis silicon source is hydrolyzed under the action of a hydrolysis catalyst, the hydrolysis catalyst is dibutyltin dilaurate, the mass ratio of the hydrolysis catalyst to the hydrolysis silicon source is 1:4, the concentration of TEOS in the PDMS-SiO2 sol is 0.002~0.02g / mL, the concentration of MTMS in the PDMS-SiO2 sol is 0.005~0.05g / mL, and the concentration of MTES in the PDMS-SiO2 sol is 0.001~0.025g / mL.

3. The method for preparing a PDMS-based double-layer hydrophobic antireflective self-cleaning coating according to claim 1 or 2, characterized in that: In step (1), the method for preparing the PDMS sol is as follows: adding PDMS and a PDMS curing agent to an organic solvent, stirring at 45-50° C. for 20-40 minutes to mix them evenly, and obtaining the PDMS sol; And / or, the hydroxylation treatment is performed by plasma treatment.

4. The method for preparing a PDMS-based double-layer hydrophobic antireflective self-cleaning coating according to claim 1, characterized in that: In step (2) and / or step (3), the dipping speed is 80-105 mm / min; and / or the drying temperature is 230-250° C., and the drying time is 40-60 min.

5. The method for preparing a PDMS-based double-layer hydrophobic antireflective self-cleaning coating according to claim 1, characterized in that: In the step (4), the outer flame carbonization treatment is selected from the outer flame of a candle, a lighter or a match; and / or the temperature of the annealing treatment is 450-500° C. and the time is 60-90 min.

6. A PDMS-based double-layer hydrophobic antireflective self-cleaning coating prepared according to the preparation method according to any one of claims 1 to 5, characterized in that: The invention comprises a PDMS connecting layer and a PDMS-SiO2 carbonized annealing layer, wherein the PDMS connecting layer is located at the bottom layer and is directly in contact with the surface of the substrate, and is obtained by dipping the substrate into a PDMS sol containing a PDMS curing agent, and the substrate is a hydroxylated substrate; The PDMS-SiO2 carbonization annealing layer is located on the top layer and connected to the PDMS connecting layer. It is obtained by dip-coating PDMS-SiO2 sol on the PDMS connecting layer, external flame carbonization, and annealing. The PDMS-SiO2 sol contains hydrophobic SiO2.

7. The PDMS-based double-layer hydrophobic antireflective self-cleaning coating according to claim 6, characterized in that: The hydrolyzed silicon source of the hydrophobic SiO2 is selected from any one of TEOS, MTMS and MTES, and the hydrolyzed silicon source is hydrolyzed under the action of a hydrolysis catalyst, the hydrolysis catalyst is dibutyltin dilaurate, the mass ratio of the hydrolysis catalyst to the hydrolyzed silicon source is 1:4, the concentration of TEOS in the PDMS-SiO2 sol is 0.002~0.02g / mL, the concentration of MTMS in the PDMS-SiO2 sol is 0.005~0.05g / mL, and the concentration of MTES in the PDMS-SiO2 sol is 0.001~0.025g / mL; and / or, the concentration of the PDMS sol is 0.08-0.16 g / ml; And / or, in the PDMS sol, the mass ratio of PDMS to PDMS curing agent is 10:

1.

8. The PDMS-based double-layer hydrophobic antireflective self-cleaning coating according to claim 6, characterized in that: The PDMS-SiO2 carbonized annealed layer has a micro-nano rough structure.

9. The PDMS-based double-layer hydrophobic antireflective self-cleaning coating according to claim 6, characterized in that: When the hydrolyzed silicon source of the hydrophobic SiO2 is selected from MTES, the PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating has a hydrophobic angle of 131.9°, a transmittance of 95.8%, and a pencil hardness of 3H.

Images