PDMS-based double-layer hydrophobic anti-reflection self-cleaning coating and preparation method thereof

Abstract

The invention provides a PDMS-based double-layer hydrophobic anti-reflection self-cleaning coating and a preparation method thereof, and relates to the technical field of hydrophobic materials, the preparation method comprises the following steps: adding polydimethylsiloxane (PDMS) and a PDMS curing agent into n-hexane, uniformly mixing to obtain PDMS sol, and dip-coating the PDMS sol on a hydroxylated substrate as a connecting layer; pDMS, a PDMS curing agent and dibutyltin dilaurate (DBTDL) are added into n-hexane, uniform mixing is performed, then tetraethoxysilane (TEOS) / methyltrimethoxysilane (MTMS) / triethoxymethylsilane (MTES) is added, PDMS-SiO2 sol is obtained, then the PDMS connection layer on the substrate is coated with the PDMS-SiO2 sol in a dip mode, and a PDMS-SiO2 hydrophobic layer is obtained; a carbonization template is introduced into a PDMS (Polydimethylsiloxane)-SiO2 hydrophobic layer by using external flame, and then annealing treatment is performed to obtain the PDMS-based double-layer hydrophobic anti-reflection self-cleaning coating, and the coating realizes coexistence of high hydrophobicity, high durability and high light transmittance.

Description

Technical Field

[0001] The invention relates to the technical field of hydrophobic materials, and 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 the leaves of many plants, the epidermis of insects, the feathers of birds and other extended parts in nature. In the 1970s, the famous botanist Bartrot first discovered the lotus effect in his research. The lotus effect mainly originated from the presence of a natural waxy hydrophobic film on its surface, which can effectively repel water droplets, so that the water droplets form approximately spherical droplets on the surface of the lotus leaf and then gather into streams without wetting the surface of the lotus leaf. At the same time, the stains on the surface of the lotus leaf are taken away. This is the lotus effect. Through this discovery, Bartrot invented the self-cleaning technology. According to existing research results, a super-hydrophobic surface refers to a material surface with a contact angle greater than 150° and a rolling angle less than 10°. A hydrophobic coating is a coating with a special surface structure. Its surface microstructure can make water droplets form an extremely high contact angle when in contact, thereby achieving the various effects we need.

[0003] As an advanced functional material, hydrophobic materials have excellent waterproof properties and bring effective solutions to different fields of production and life. From the application point of view, when the hydrophobic surface has multiple functions such as transparency, photocatalysis and self-healing after damage, it will become very useful. Through the engineering surface structure technology, nearly spherical water droplets are formed to roll down, and dust, mold and bacteria can be effectively removed during the rolling process. Self-cleaning technology has been widely accepted and widely used in optical devices, buildings and various industrial facilities. In the construction industry, the application of hydrophobic coatings can effectively improve the waterproof performance of structures such as walls and roofs, extend the service life of houses, and reduce maintenance costs; in the field of transportation, whether it is automobiles, ships or aircraft, the use of hydrophobic materials can effectively prevent moisture from adhering, improve running speed and safety; in the textile industry, by learning hydrophobic technology, textile products with excellent waterproof functions are developed to meet consumers' dual needs for functionality and comfort; in the electronics field, hydrophobic materials provide effective protection measures for electronic equipment and components, prevent short circuits and damage caused by moisture, and extend the service life of electronic products. However, the key to the hydrophobic performance of hydrophobic materials is durability. In particular, in some fields, the color of the substrate must be maintained, which requires the hydrophobic material to have high light transmittance. Therefore, in order to obtain a coating material with self-cleaning properties and good hydrophobicity that takes into account both high light transmittance and durability, the present invention is proposed. Summary of the invention

[0004] In view of 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 it is difficult for the hydrophobic coating 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 the first aspect, a method for preparing a PDMS-based double-layer hydrophobic anti-reflective 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 later use;

[0008] (2) dip-coating the PDMS sol on a prepared substrate, and obtaining a PDMS connecting layer after drying;

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

[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] Further, in step (1), 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; and / or, the hydrolysis silicon source of the hydrophobic SiO2 is selected from any one of TEOS, MTMS and MTES, and 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 0.002-0.02 g / mL, the concentration of MTMS in the PDMS-SiO2 sol is 0.005-0.05 g / mL, and the concentration of MTES in the PDMS-SiO2 sol is 0.001-0.025 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, thereby obtaining the PDMS sol;

[0013] 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. for 20 to 40 minutes; then a hydrolysis silicon source is added, and stirred again at a temperature of 40 to 45° C. for 60 to 75 minutes to obtain 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 to 500° C. and the time is 60 to 90 minutes.

[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 directly in 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;

[0018] The PDMS-SiO2 carbonization annealing layer is located at 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 hydrolysis silicon source is 1:4. More preferably, the concentration of TEOS in the PDMS-SiO2 sol is 0.002-0.02 g / mL, the concentration of MTMS in the PDMS-SiO2 sol is 0.005-0.05 g / mL, and the concentration of MTES in the PDMS-SiO2 sol is 0.001-0.025 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 carbonization annealing 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 bottom layer of a PDMS connecting layer and a top layer of a PDMS-SiO2 carbonization annealing layer, thereby obtaining a high durability characteristic. At the same time, the PDMS-SiO2 carbonization annealing 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 carbonization annealing layer is significantly higher than that of the PDMS carbonization annealing coating and the PDMS coating, and can reach about 95%. In the specific preparation, a pull-up and immersion dip coating method can be used in conjunction with a 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 the hydrophobic coating to achieve the coexistence of hydrophobicity, durability and high light transmittance.

[0026] (2) The present invention selects to use MTMS / MTES to prepare nano-SiO2, and 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-reflection self-cleaning coating of the present invention is prepared, when the nano-SiO2 is prepared by adding MTES hydrolysis, the overall performance results of the coating are 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 photovoltaic, solar energy, ships, wind turbine blades and other devices. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[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, wherein 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 scheme and advantages of the present invention clearer, the technical scheme in the embodiment 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 only 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 ordinary technicians in the field without making creative work are within the scope of protection of the present invention. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0033] The endpoints and any values ​​of the ranges disclosed in the present invention 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 endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0034] In the present invention, unless otherwise specified and / or described, all numerical values ​​involving content are "mass values ​​or volume values ​​or concentration values" from beginning to end. The process parameters without specific conditions in the following examples are usually based on conventional conditions. The raw materials described in the following examples can all be obtained from public commercial channels.

[0035] According to a first aspect of the present invention, the present invention provides a method for preparing a PDMS-based double-layer hydrophobic anti-reflective 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 later use;

[0037] (2) dip-coating the PDMS sol on a prepared substrate, and obtaining a PDMS connecting layer after drying;

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

[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-transmittance self-cleaning coating with a double-layer structure prepared by the method of the present invention has better durability, light transmittance and hydrophobicity than a single-layer PDMS coating. After extensive research, the inventor found that although the hydrophobicity and light transmittance of the single-layer PDMS coating are increased after carbonization annealing, and the light transmittance is increased to about 92%, the pencil hardness of the single-layer PDMS carbonization annealing coating is poor, only B, and the durability cannot be well taken into account, and the light transmittance needs to be strengthened. By constructing a double-layer composite structure with a PDMS connecting layer as the bottom layer and a PDMS-SiO2 carbonization annealing layer as the top layer, the pencil hardness of the PDMS carbonization annealing coating can be improved, that is, a high durability characteristic can be obtained. At the same time, the PDMS-SiO2 carbonization annealing layer is prepared using raw materials that can generate hydrophobic SiO2 in situ, which can not only improve the hydrophobicity of the PDMS coating, but also significantly improve the light transmittance of the PDMS coating. Even after carbonization and blackening, annealing and then transparent, the light transmittance of the double-layer coating can still reach about 95%. In the specific preparation, the pull-up and immersion dip coating method can be used in conjunction with the carbonization annealing treatment to achieve the preparation of the hydrophobic coating with high hydrophobicity, high durability and high light transmittance, and the preparation process is simple. The method of the present invention solves the problem that it is difficult for the hydrophobic coating in the prior art to achieve the coexistence of hydrophobicity, durability and high light transmittance.

[0041] The technical mechanism of the present invention is as follows: the coating sol, i.e., PDMS sol and PDMS-SiO2 sol, are sequentially attached to a hydroxylated substrate such as a plasma-treated glass slide by a dip coating method, and a double-layer composite structure is constructed to enable the coating to achieve high durability. The hydrophobicity provided by the present invention comes from two aspects: one is the micro-nano structure provided by nano-SiO2 obtained by hydrolysis of a hydrolyzed silicon source such as tetraethyl orthosilicate (TEOS) / methyltrimethoxysilane (MTMS) / triethoxymethylsilane (MTES), and the other is the rough structure provided by the introduction of a carbonized template to achieve hydrophobicity. Although the carbonized template increases the hydrophobicity, the coating becomes black when the carbonized template is introduced, so an annealing treatment is performed to allow the blackened coating to volatilize by generating CO2 at high temperature and then restore 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 limitedly selected as 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, and 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, 0.04 g / ml, 0.06 g / ml, 0.08 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 (for example, 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 solution realizes the high light transmittance of the composite coating by TEOS / MTMS / MTES, because TEOS / MTMS / MTES itself has an anti-reflection effect, which provides a new direction for designing a hydrophobic anti-reflection self-cleaning coating. In addition, whether the hydrolyzed silicon source is TEOS or MTMS or MTES, the SiO2 in the coating is generated in situ, is nano-scale, and has hydrophobicity. And further, MTMS / MTES is selected to prepare nano-SiO2, which has better hydrophobicity, because MTMS / MTES has a hydrophobic methyl group, so that the prepared nano-SiO2 has a methyl group that is hydrophobically modified in situ, and has a better hydrophobicity than the nano-SiO2 prepared by TEOS.

[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: adding PDMS and a PDMS curing agent to an organic solvent, stirring at 45 to 50° C. (such as 46° C., 47° C., 48° C., 49° C.) for 20 to 40 minutes (such as 25 minutes, 30 minutes, 35 minutes) to mix them evenly, thereby obtaining the PDMS sol;

[0046] And / or, the method for preparing PDMS-SiO2 sol is as follows: add PDMS, PDMS curing agent and hydrolysis catalyst to an organic solvent, stir and treat 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 add a hydrolysis silicon source, stir and treat 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 PDMS-SiO2 sol;

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

[0048] In the above technical scheme, the control of the temperature and reaction time of the stirring treatment is to fully mix, especially during the hydrolysis reaction, the reaction fully generates SiO2, but the temperature and time have little effect. The low temperature leads to a long hydrolysis time, 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 high temperature hydrolysis will be too fast and may cause the nano-SiO2 to clump and become rough.

[0049] The purpose of the hydroxylation treatment of the substrate is to make the hydroxyl groups (-OH) on the substrate surface react with the silanol groups (Si-OH) in the coating sol to form Si-O-Si, so as to increase the adhesion between the substrate and the coating. Hydroxylation treatment can also be carried out by other methods other than plasma treatment, as long as the substrate surface can be 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 achieve the dissolution of related raw materials and volatilization when the coating is dried, such as: n-hexane, 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 scheme, a dipping method of pulling and dipping can be used, and 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, no specific requirements are made 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 annealing treatment is carried out at a temperature of 450 to 500°C (e.g., 455°C, 460°C, 465°C, 470°C, 475°C, 480°C, 485°C, 490°C, 495°C), and the time is 60 to 90 min (e.g., 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 an outer flame that is in full contact with the air to carbonize the PDMS in the coating to obtain a rough structure and increase 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 end, horizontally pass through the top of the candle flame, i.e., the candle outer flame, to carbonize the PDMS. The carbonization temperature is the candle outer flame temperature. The coating surface is completely blackened after being burned by the outer flame from one end to the other end, indicating that the carbonized template is introduced. The coating with the carbonized template introduced is placed in a muffle furnace for annealing treatment. The annealing temperature is 450-500°C and the time is 60-90min, so that the carbonized template generates carbon dioxide (CO2) at high temperature and volatilizes, 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 with the coating formed by simple dip coating and drying before carbonization annealing, 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. During annealing, the temperature and time need to be controlled within the aforementioned range, which can avoid the annealing temperature being too low within the same annealing time, which will leave the carbonized template and the transmittance will not meet the requirements, and can 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 anti-reflective self-cleaning coating, comprising a PDMS connecting layer and a PDMS-SiO2 carbonization annealing layer, wherein the PDMS connecting layer is located at the bottom layer, is directly in contact with and connected to the surface of a substrate, and is obtained by dip-coating a PDMS sol containing a PDMS curing agent on the substrate, wherein the substrate is a hydroxylated substrate;

[0057] The PDMS-SiO2 carbonization annealing layer is located at 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 anti-reflective 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 0.002-0.02 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 0.002-0.02 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 implementation 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 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.

[0064] The following is an explanation with reference to specific embodiments and comparative examples.

[0065] The sources of the reagents used in the experiment of the present invention are: polydimethylsiloxane (PDMS) (Dow Corning, specification DC184), PDMS curing agent (Dow Corning, specification SYLGARD184), dibutyltin dilaurate (Shanghai McLean Biochemical Technology Co., Ltd., specification analytical grade), MTES and MTMS (Shanghai McLean 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, wherein the preparation method comprises 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) into 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), wherein SiO2 is hydrophobic SiO2, nanometer-scale, 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 sheet (glass slide). During dip coating, the glass sheet is completely immersed in the sol. The dipping speed is 90 mm / min and the holding time is 30 seconds. Then the glass sheet 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 sheet 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, place the glass sheet in a muffle furnace and bake 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 the carbonized template. Use tweezers to clamp the glass sheet, 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 carbonized template is successfully introduced to obtain a coating containing a PDMS connecting layer and a PDMS-SiO2 carbonized layer (PDMS / PDMS-TEOS carbonized coating); then place the glass sheet with the introduced carbonized template in a muffle furnace for annealing treatment at an annealing temperature of 450-500°C for 60-90 minutes, so that the carbonized 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-TEOS carbonized annealing coating) containing a PDMS connecting layer and a PDMS-SiO2 carbonized 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) into 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), wherein SiO2 is hydrophobic SiO2, nanometer-sized, 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 sheet (glass slide). During dip coating, the glass sheet is completely immersed in the sol. The dipping speed is 90 mm / min and the holding time is 30 seconds. Then the glass sheet 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 sheet 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, place the glass sheet in a muffle furnace and bake 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 the carbonized 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 carbonized template is successfully introduced to obtain a coating containing a PDMS connecting layer and a PDMS-SiO2 carbonized layer (PDMS / PDMS-MTMS carbonized coating); then place the glass slide with the introduced carbonized template in a muffle furnace for annealing treatment at an annealing temperature of 450-500°C for 60-90 minutes, so that the carbonized 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 carbonized annealing coating) containing a PDMS connecting layer and a PDMS-SiO2 carbonized 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) into 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), wherein SiO2 is hydrophobic SiO2, nanometer-sized, 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 sheet (glass slide). During dip coating, the glass sheet is completely immersed in the sol. The dipping speed is 90 mm / min and the holding time is 30 seconds. Then the glass sheet 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 sheet 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, place the glass sheet in a muffle furnace and bake 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 carbonized 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 carbonized template is successfully introduced to obtain a coating containing a PDMS connecting layer and a PDMS-SiO2 carbonized layer (PDMS / PDMS-MTES carbonized coating); then place the glass slide with the introduced carbonized template in a muffle furnace for annealing treatment at an annealing temperature of 450-500°C for 60-90 minutes, so that the carbonized 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-MTES carbonized annealing coating) containing a PDMS connecting layer and a PDMS-SiO2 carbonized annealing layer.

[0087] Comparative Example 1

[0088] The difference from Example 1 is that there are no steps 2 and 4, and 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 sheet (glass slide). During dip coating, the glass sheet is completely immersed in the sol. The dipping speed is 90 mm / min and the holding time is 30 seconds. Then the glass sheet 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 sheet 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 the carbonized 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 carbonized template is successfully introduced to obtain the PDMS carbonized coating; then place the glass sheet with the introduced carbonized template in a muffle furnace for annealing treatment. The annealing temperature is 450-500°C and the time is 60-90 minutes, so that the carbonized template generates carbon dioxide (CO2) at high temperature and evaporates, and finally a transparent PDMS hydrophobic self-cleaning coating (PDMS carbonized annealed 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, 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 horizontally and evenly, so that the dust is evenly sprinkled on the test surface of the glass slide, and drip water from one end of the test surface to perform a self-cleaning test of the coating.

[0096] The test results show that the dust-repelling ability of the coated glass surface is significantly better than that of the blank glass. When water droplets roll on the coated glass, they can successfully remove the dust on the surface, thus keeping the glass clean. This fully proves that these coating samples have excellent self-cleaning ability. Further observations reveal that water droplets can form tiny vortices on the coating surface during the rolling process. These vortices effectively carry away impurities on the coating surface along with the water droplets. It can be seen that these coatings are hydrophobic and can self-clean. After being attached to the glass surface, they can realize the self-cleaning function of the glass.

[0097] (2) Hydrophobic angle test analysis

[0098] In order to further explore the hydrophobicity of the coating, the present invention uses a contact angle meter to measure the contact angle of water droplets on coatings with different raw material ratios. Specifically, a drop of deionized water is dropped on the surface of the sample coating with a needle, and the size of the contact angle between the water droplet and the coating surface is observed and analyzed to characterize the hydrophobicity of the sample surface coating.

[0099] like Figure 1As shown in Figure 2, ad are the hydrophobic angles of the single-layer PDMS coating, double-layer PDMS / PDMS-TEOS coating, PDMS / PDMS-MTMS coating and PDMS / PDMS-MTES coating formed by dip-coating PDMS, PDMS-TEOS, PDMS-MTMS and PDMS-MTES sol, 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 water 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. The hydrophobic angles are 158.8°, 157.6°, and 114.7°, respectively, compared with the hydrophobic angle range of 114.7°-119.5° of the coating obtained by simple dip-coating and drying. 160.8°, 161.2°, which shows that the carbonization template is successfully introduced, the carbonization template has a rough structure, and the carbonization template is used to make the coating have a rough structure to achieve a superhydrophobic effect; il is a single-layer PDMS carbonization annealing 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 carbonization annealing coating, PDMS / PDMS-MTMS carbonization annealing coating and PDMS / PDMS-MTES carbonization annealing coating. The hydrophobic angles are 133.2°, 130.5°, 120.7°, and 131.9°, respectively. Although the carbonized template generates CO2 volatilization by high-temperature baking to restore transparency, the hydrophobic angle is reduced compared with the introduction of the carbonized template, and is increased compared with the dip coating, indicating that the volatilization of carbon dioxide during annealing will affect the roughness of the coating to a certain extent, but 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-reflection self-cleaning coating of the present invention has better hydrophobicity than the single-layer PDMS coating.

[0100] The above test results of the hydrophobic angle 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 The following are the transmittance test diagrams of the bare glass slide and the PDMS coating attached to the glass slide, the single-layer PDMS carbonized annealed coating after carbonization annealing, the double-layer PDMS / PDMS-TEOS carbonized annealed coating, the PDMS / PDMS-MTMS carbonized annealed coating, and the PDMS / PDMS-MTES carbonized annealed coating. As shown in the figure, the maximum transmittance in the visible light range is as follows: the bare glass transmittance is 91%; a is a single-layer PDMS carbonized annealed coating, and its transmittance is 92.6%; b is a double-layer PDMS / PDMS-TEOS carbonized annealed coating, and its transmittance is 94.7%; c is a double-layer PDMS / PDMS-MTMS carbonized annealed coating, and its transmittance is 96%; d is a double-layer PDMS / PDMS-MTES carbonized annealed coating, and its transmittance is 95.8%; e is a PDMS coating, and its transmittance is 89%. Compared with the bare glass slide, the transmittance of the PDMS coating formed by the PDMS sol decreased. Although it increased after carbonization annealing, it was still not as transparent as the glass slide that was dip-coated with the PDMS sol and the PDMS-SiO2 sol and then carbonized annealed. This shows that the TEOS, MTMS, and MTES added to the double-layer structure have an anti-reflection effect, achieving the high light transmittance of the coating. In addition, the light transmittance of the PDMS-based double-layer hydrophobic anti-reflection self-cleaning coating of the present invention is much better than that of the PDMS coating.

[0104] (4) Pencil hardness test analysis

[0105] According to the standard test method for coating performance (GBT6739), the hardness of the hydrophobic coating is evaluated by whether a pencil scratch can break through the coating, and the maximum hardness of the pencil lead that the coating can withstand is tested (divided from 6B to 6H from soft to hard). The pencil hardness of different composite coatings measured has different values, among which the pencil hardness of the single-layer PDMS carbonized annealed coating is B, while the pencil hardness of the double-layer PDMS / PDMS-TEOS carbonized annealed coating reaches 3H, the pencil hardness of the PDMS / PDMS-MTMS carbonized annealed coating reaches 4H, and the pencil hardness of the PDMS / PDMS-MTES carbonized annealed coating reaches 3H, indicating that the pencil hardness of the coating is improved by constructing a double-layer composite structure, so 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 has high hydrophobicity, high durability and high light transmittance, which solves the problem that the hydrophobic coating in the prior art is difficult to achieve the coexistence of hydrophobicity, durability and high light transmittance. In addition, 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, the overall performance results of the coating are relatively better, the hydrophobic angle is 131.9°, the light transmittance is 95.8%, and the pencil hardness is 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned 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 anti-reflective self-cleaning coating, characterized in that: The following steps are involved: (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 later use; (2) dip-coating the PDMS sol on a prepared substrate, and obtaining a PDMS connecting layer after drying; (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 anti-reflective self-cleaning coating according to claim 1, characterized in that: In step (1), 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; and / or, the hydrolysis silicon source of the hydrophobic SiO2 is selected from any one of TEOS, MTMS and MTES, and 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 0.002-0.02 g / mL, the concentration of MTMS in the PDMS-SiO2 sol is 0.005-0.05 g / mL, and the concentration of MTES in the PDMS-SiO2 sol is 0.001-0.025 g / mL; and / or, the hydrophobic SiO2 is nanoscale.

3. The method for preparing a PDMS-based double-layer hydrophobic anti-reflective 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 to 50° C. for 20 to 40 minutes to mix them evenly, and obtaining the PDMS sol; 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. for 20 to 40 minutes; then a hydrolysis silicon source is added, and stirred again at a temperature of 40 to 45° C. for 60 to 75 minutes to obtain PDMS-SiO2 sol; And / or, the hydroxylation treatment is performed by plasma treatment.

4. The method for preparing a PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating according to claim 1, characterized in that: 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.

5. The method for preparing a PDMS-based double-layer hydrophobic anti-reflective 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 anti-reflective self-cleaning coating, characterized in that: It comprises a PDMS connecting layer and a PDMS-SiO2 carbonization annealing layer, wherein the PDMS connecting layer is located at the bottom layer, is directly in contact with and connected to the surface of the substrate, and is obtained by dipping the substrate into a PDMS sol containing a PDMS curing agent, wherein the substrate is a hydroxylated substrate; The PDMS-SiO2 carbonization annealing layer is located at 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 anti-reflective self-cleaning coating as claimed in claim 6, characterized in that: Prepared according to any one of claims 1 to 5.

8. The PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating as claimed in claim 6, characterized in that: 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 0.002-0.02 g / mL, the concentration of MTMS in the PDMS-SiO2 sol is 0.005-0.05 g / mL, and the concentration of MTES in the PDMS-SiO2 sol is 0.001-0.025 g / mL; and / or, the hydrophobic SiO2 is nanoscale; and / or, 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.

9. The PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating as claimed in claim 6, characterized in that: The PDMS-SiO2 carbonization annealing layer has a micro-nano rough structure.

10. The PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating according to claim 6, characterized in that: 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.

Images