Preparation method of SiO2 film with high light transmittance, low haze and super hydrophobicity

Abstract

The application relates to a SiO2 film preparation method with high light transmittance, low haze and super hydrophobicity, and belongs to the technical field of functional films. The method comprises the following steps: preparing SiO2 sol by using an alkali catalysis method; mixing the SiO2 sol with tetrahydrofuran, sequentially adding a silane coupling agent and a Dow Corning optical glue solution, and coating films on transparent organic glass and silicate glass respectively, and drying and curing at room temperature; placing the glass containing the film and perfluorosilane in a sealed container, and evaporating the perfluorosilane to the film surface for fluorination treatment under certain temperature and time, so that the SiO2 film with high light transmittance, low haze, super hydrophobicity and firm combination is obtained. The ingenious coordination of various strategies is an important factor for realizing the application purpose. The preparation method provided by the application is low in raw material cost, does not need high-temperature heat treatment, and is simple in operation process, is suitable for film coating of large-size special-shaped parts, can be applied on various transparent substrates, and can maintain long-time high-visibility scenes in indoor and outdoor environments.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a high-transmittance, low-haze and super-hydrophobic SiO2 film. BACKGROUND

[0002] Superhydrophobic transparent films are thin films that possess both water resistance or repellency and high light transmittance. Water resistance refers to the ability of a coating to effectively prevent water from penetrating to the surface of the substrate beneath the coating, thereby preventing damage to the substrate caused by water. Water repellency refers to the ability of a coating to resist water intrusion or surface contact with water for a short period of time, preventing water from remaining on the surface of the coating or quickly expelling water droplets, thereby not damaging the coating. These films are typically applied to surfaces to make the material or device surface superhydrophobic, capable of resisting the adhesion of water or other polar liquids, while not reducing or even enhancing light transmittance. This film technology has been widely applied in various fields, including solar cells, medical devices, optical elements, and display technology. Sol-gel method is a common method for preparing superhydrophobic antireflection films, which has the advantages of simple preparation process and suitability for large-area film preparation. To date, researchers have reported many methods for preparing superhydrophobic antireflection SiO2 films using the sol-gel method, such as: Jiajie Yu, Binrui Wu, Nan Wu, Chaoyi Peng, Jun Yang, Yunyun Meng, Suli Xing. Chemical Engineering Journal, 2021, 404, 1385-8947; [2] Siddiqui, Wen Li, Fajun Wang, Junfei Ou, Amirfazli. Applied Surface Science, 2021, 542, 0169-4332. There are also many patents related to superhydrophobic transparent films (CN201910723543.9, CN202211141538.5, CN116333592A, CN201811297045.4). The methods involved include sol-gel method, chemical vapor deposition method, and physical vapor deposition method. However, these preparation methods are limited to coordinating the relationship between light transmittance and superhydrophobicity. There is no report on a technology that takes into account the coordination between haze, light transmittance, and superhydrophobicity. According to the corresponding optical theory, high light transmittance does not mean good visual field effect, especially for some fields that have special requirements for visual line, such as medical devices, visible / infrared photosensitive devices, etc. Haze has a profound impact on the visibility and safety of the device. Therefore, it is extremely important to coordinate the haze on the basis of transparency and superhydrophobicity. According to the theory, there is a certain contradictory relationship between the light transmittance, superhydrophobicity, and haze of the film. In order to coordinate the light transmittance and superhydrophobicity, it is necessary to accurately control the size of the film particles and their agglomerates, maintaining them within the Rayleigh scattering region, i.e. less than the wavelength of visible light. In this case, Rayleigh scattering caused by particles does not change the transmission direction of light, so it does not negatively affect light transmittance. However, once the haze performance indicator is considered, the situation becomes complex.To control the propagation direction of the transmitted light, the particle size needs to be further reduced and agglomeration is inhibited. It should be noted that the smaller the particle size is not necessarily better. Generally, other modifiers need to be introduced to meet other performance requirements, such as the bonding force of the film and superhydrophobicity. If the particle size is too small, uncontrollable agglomeration between the particles can occur, which eventually forms an uneven film surface after film formation. Such uneven accumulation and agglomeration, although beneficial to achieving superhydrophobicity, can greatly increase the haze. Therefore, the method of coordinating between the transmittance, superhydrophobicity and haze lies in reducing the particle size while ensuring uniform distribution of the particles in the film and enhancing the superhydrophobic properties of the particle surface to maintain the overall performance of the film. SUMMARY

[0003] The purpose of the present application is to provide a simple and controllable method for preparing a SiO2 film with high transmittance, low haze and superhydrophobicity. By the method of the present application, the nano-SiO2 sol particles can maintain high dispersibility, and uniform accumulation of the SiO2 particles on the surface of the substrate can be achieved. The transmittance and contact angle of the film prepared by the method of the present application are both improved, and the haze of the film is basically unchanged. At the same time, the film and the substrate also have excellent bonding force.

[0004] A method for preparing a SiO2 film with high transmittance, low haze and superhydrophobicity, characterized in that the method comprises the following steps: preparing SiO2 sol by alkali catalysis, adjusting the SiO2 particle size, modifying the SiO2 with a mixture of tetrahydrofuran, water and ethanol as the solvent, using Dow Corning optical glue and silane coupling agent, coating the film by dip-coating method, and then performing surface treatment with perfluorosilane as the fluorination agent. The combination of the above steps is an important factor for achieving the purpose of the present application. The prepared film has superhydrophobicity, high transmittance and low haze, and excellent bonding force with the substrate.

[0005] The method for preparing a SiO2 film with high transmittance, low haze and superhydrophobicity comprises the following steps:

[0006] (1) adding tetraethyl orthosilicate to an ethanol solution containing deionized water and ammonia, and treating in a water bath at 40-70℃ for 4-12h to obtain SiO2 sol; wherein the preferred volume ratio of tetraethyl orthosilicate: ammonia: ethanol: deionized water is (3-12)ml: (1-4)ml: (40-110)ml: (2-8)ml;

[0007] The particle size of SiO2 in the SiO2 sol is any two of 10nm, 20nm, 30nm and 40nm, and further preferably the volume ratio of the SiO2 sol with relatively smaller particle size to the SiO2 sol with relatively larger particle size is 17:3-1:1.

[0008] The main agent and the auxiliary agent of the Dow Corning optical glue (the optical glue is composed of a main agent and an auxiliary agent, the main agent is polydimethylsiloxane, and the auxiliary agent is a crosslinking agent. The crosslinking agent is a mixture containing dimethyl methyl hydrogen, vinyl-terminated dimethyl polysiloxane, vinyl MQ resin mixture, tetramethyl tetra-vinyl cyclo tetra siloxane, etc.) are mixed, then tetrahydrofuran is added, and ultrasonic dissolution is performed to obtain a Dow Corning optical glue solution. The type of the Dow Corning optical glue is preferably DC184, and the amount is preferably main agent: auxiliary agent: tetrahydrofuran = (1-2) g: (0.1-0.4) g: (10-20) ml.

[0009] (2) The tetrahydrofuran, the silane coupling agent, and the Dow Corning optical glue solution are added into the SiO2 sol respectively, and stirring is performed at room temperature for 18-32 h to obtain a modified SiO2 sol; the silane coupling agent is preferably one of γ-mercaptopropyl trimethoxysilane, γ-mercaptopropyl trimethoxysilane, γ-glycidyl ether propyl trimethoxysilane, and γ-methacryloyloxy propyl trimethoxysilane, and the amount of each substance in the modified SiO2 sol is in a volume ratio of SiO2 sol: tetrahydrofuran: silane coupling agent: Dow Corning optical glue solution = (10-20):(10-20):(0.05-0.1):(0.4-0.6);

[0010] (3) The glass substrate is sequentially subjected to ultrasonic treatment in deionized water and an ethanol solution for 1-2 min, and then taken out and dried for standby use. The glass is any inorganic glass or organic glass;

[0011] (4) The film is prepared by using the dip-coating method, the pulling speed is 500-2000 μm / s, the pulling times are 2-8 times, the dipping time is 1-3 min, and the film is cured at room temperature for 18-32 h after being formed;

[0012] (5) The substrate containing the film and the perfluorosilane are placed in a sealed container, the perfluorosilane is evaporated to the surface of the film at a certain temperature to perform surface fluorination treatment, and the high-transmittance, low-haze, and super-hydrophobic SiO2 film is obtained;

[0013] The perfluorosilane is preferably one of heptadecafluorodecyl trimethoxysilane, tridecafluorooctyl trimethoxysilane, and dodecafluoroheptyl propyl trimethoxysilane. The amount of the perfluorosilane is 0.05 ml per 48 cm 2 The amount of the perfluorosilane corresponding to the film area is 0.05 ml, the fluorination treatment temperature is preferably 30-80 ℃, and the treatment time is preferably 12-24 h.

[0014] The application provides a super-hydrophobic SiO2 film with high light transmittance, low haze and excellent adhesion to the substrate. The preparation method provided by the application has low cost, does not need high-temperature heat treatment and simple operation process, is suitable for film coating of large-size special-shaped parts, can be applied to various transparent substrates, maintains high perspective scenes for a long time in indoor and outdoor environments, and has high application prospect and use value. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a TEM image of the SiO2 sol in Example 1. In the figure, the average particle size of SiO2 can be adjusted to about 10 nm, 20 nm, 30 nm or 40 nm, and the particle dispersion is high.

[0016] Figure 2 It is a diagram of the fluorination treatment device for the film surface in Examples 2-7.

[0017] Figure 3 It is a digital photo of the pure glass substrate and the glass containing the SiO2 film in Example 2. In the figure, the perspective effect is unchanged before and after the film coating, indicating that the film has excellent light transmittance.

[0018] Figure 4 It is a SEM image of the SiO2 film in Example 2. In the figure, the SiO2 particles after film formation are uniformly stacked without agglomerated particles.

[0019] Figure 5 It is an AFM image of the pure peeled substrate and the glass containing the SiO2 film in Example 2. In the figure, the roughness changes only slightly before and after the film coating, indicating that the film is very smooth and flat.

[0020] Figure 6 It is a comparison of the light transmittance test results of the pure glass substrate and the glass containing the SiO2 film in Examples 2-7.

[0021] Figure 7 It is the haze test results of the pure glass substrate and the glass containing the SiO2 film in Examples 2-7. Figure 8 It is a comparison of the contact angle test results of the pure glass substrate and the glass containing the SiO2 film in Examples 2-7.

[0022] Figure 9 It is an optical microscope image before and after the adhesion rating test in Example 2.

[0023] Table 1 is the adhesion rating results of the inorganic glass containing the SiO2 film in Examples 2-7 according to the national standard GBT9286-1998.

[0024] Table 2 is the adhesion rating results of the organic glass containing the SiO2 film in Examples 2-7 according to the national standard GBT9286-1998. DETAILED DESCRIPTION

[0025] The application will be further described in connection with the following examples, which do not limit the application.

[0026] Example 1:

[0027] 40 ml of ethanol, 3 ml of tetraethyl orthosilicate, 2 ml of water, and 1 ml of ammonia were added into a beaker, stirred at room temperature for 10 min, and water-bathed at 70°C for 4 h to obtain a SiO2 sol with an average particle size of 10 nm.

[0028] 110 ml of ethanol, 9 ml of tetraethyl orthosilicate, 4 ml of water, and 2 ml of ammonia were added into a beaker, stirred at room temperature for 10 min, and water-bathed at 60°C for 12 h to obtain a SiO2 sol with an average particle size of 20 nm.

[0029] 60 ml of ethanol, 6 ml of tetraethyl orthosilicate, 8 ml of water, and 3 ml of ammonia were added into a beaker, stirred at room temperature for 10 min, and water-bathed at 70°C for 6 h to obtain a SiO2 sol with an average particle size of 30 nm.

[0030] 80 ml of ethanol, 12 ml of tetraethyl orthosilicate, 6 ml of water, and 2 ml of ammonia were added into a beaker, stirred at room temperature for 10 min, and water-bathed at 50°C for 8 h to obtain a SiO2 sol with an average particle size of 40 nm.

[0031] Example 2:

[0032] Dow Corning DC184 optical glue was mixed and stirred according to 1 g of main agent and 0.4 g of auxiliary agent until a large amount of bubbles were generated, 10 ml of tetrahydrofuran was then added, and ultrasonic treatment was performed for 10 min to obtain a Dow Corning DC184 solution.

[0033] 20 ml of SiO2 sol (particle size distribution of 10 nm:20 nm = 16 ml:4 ml) in Example 1, 10 ml of tetrahydrofuran, 0.1 ml of γ-mercaptopropyl triethoxysilane, and 0.6 ml of Dow Corning DC184 solution were added into a beaker, stirred at room temperature for 24 h to obtain a modified SiO2 sol.

[0034] The film was coated on transparent organic glass (PMMA) and silicate glass by dip-coating method, the pulling speed was 500 μm / s, the pulling number was 8 times, the dipping time was 1 min, and the curing time was 18 h.

[0035] The substrate (coating area of 48 cm 2 , 6 cm x 8 cm) with the film was placed in a sealed container together with 0.05 ml of heptadecafluorodecyl trimethoxysilane, and the film was subjected to surface fluorination treatment at 80°C for 12 h to obtain a SiO2 film with high light transmittance, low haze, and super-hydrophobicity.

[0036] All examples were tested for transmittance, haze, contact angle, adhesion using the same method. The transmittance test method is as follows: the transmittance (T T ) was measured using a Uv-vis ultraviolet visible spectrophotometer, and the average visible light transmittance (380-780 nm) was calculated according to the national standard GB / T 2680-2021. The haze test method is as follows: the scattered transmittance (T D ) and total transmittance (T T ) were measured using a Uv-vis ultraviolet visible spectrophotometer, and the haze was tested according to the national standard GB / T 2410-2008, with the test standard being the ratio of diffuse transmittance and total transmittance T T is the average total transmittance; T D is the average scattered transmittance. The contact angle test method is as follows: the contact angle was tested using an SZ-CAMB1 static contact angle measuring instrument, three points were tested for each sample, and the average value was taken. The adhesion test method is as follows: the adhesion of the film was rated using the national standard GB / T9286-1998, a knife edge was used to draw 10 lines on the film surface in the vertical and horizontal directions to form a grid, each line was spaced 1 mm apart, then a 3M pressure-sensitive tape was placed in the center of the grid, pressed until the tape changed color to indicate complete contact, then the tape was removed, and the film was judged according to the grid to determine the grade.

[0037] Example 3:

[0038] Dow Corning DC184 optical glue was mixed and stirred according to the main agent 1 g, the auxiliary agent 0.1 g until a large amount of bubbles were produced, then 20 ml of tetrahydrofuran was added, and ultrasonic treatment was performed for 10 min to obtain a Dow Corning DC184 solution.

[0039] 10 ml of SiO2sol (particle size distribution was 10 nm: 30 nm = 7 ml: 3 ml), 20 ml of tetrahydrofuran, 0.05 ml of γ-mercaptopropyltrimethoxysilane, and 0.6 ml of Dow Corning DC184 solution were taken from Example 1 and added to a beaker, stirred at room temperature for 18 h to obtain a modified SiO2sol.

[0040] The dip-coating method was used to coat films on transparent organic glass (PMMA) and silicate glass, the pulling speed was 2000 μm / s, the pulling number was 2 times, the dipping time was 3 min, and the curing time was 32 h.

[0041] The substrate containing the film (the film area was 48 cm 2 , 6 cm x 8 cm) and 0.05 ml of heptadecafluorodecyltrimethoxysilane were placed in a sealed container, and the surface of the film was fluorinated at 30°C for 24 h to obtain a high transmittance, low haze, and super-hydrophobic SiO2film.

[0042] Example 4:

[0043] Mixing and stirring the Dow Corning DC184 optical glue according to the main agent 2g, the auxiliary agent 0.2g to produce a large number of bubbles, then adding 10ml tetrahydrofuran, and ultrasonic for 10min to obtain the Dow Corning DC184 solution.

[0044] Taking 20ml SiO2sol (particle size distribution is 10nm:40nm=17ml:3ml), 10ml tetrahydrofuran, 0.08ml γ-glycidoxypropyltrimethoxysilane, 0.6ml Dow Corning DC184 solution in a beaker, stirring for 24h at room temperature to obtain the modified SiO2sol.

[0045] The dip-coating method is used to coat the film on the transparent organic glass (PMMA) and silicate glass, the pulling speed is 1200μm / s, the pulling times is 4, the dipping time is 2min, and the curing time is 24h.

[0046] The substrate containing the film (the film area is 48cm 2 , 6cm×8cm) and 0.05ml heptadecafluorodecyltrimethoxysilane are put into a sealed container, and the surface fluorination treatment of the film is carried out at 60℃ for 20h to obtain the high light transmittance, low haze and super-hydrophobic SiO2film.

[0047] Example 5:

[0048] Mixing and stirring the Dow Corning DC184 optical glue according to the main agent 1g, the auxiliary agent 0.2g to produce a large number of bubbles, then adding 10ml tetrahydrofuran, and ultrasonic for 10min to obtain the Dow Corning DC184 solution.

[0049] Taking 15ml SiO2sol (particle size distribution is 20nm:30nm=12ml:3ml) in Example 1, 15ml tetrahydrofuran, 0.05ml γ-methacryloyloxypropyltrimethoxysilane, 0.4ml Dow Corning DC184 solution in a beaker, stirring for 24h at room temperature to obtain the modified SiO2sol.

[0050] The dip-coating method is used to coat the film on the transparent organic glass (PMMA) and silicate glass, the pulling speed is 1200μm / s, the pulling times is 4, the dipping time is 2min, and the curing time is 18h.

[0051] The substrate containing the film (the film area is 48cm 2 , 6cm×8cm) and 0.05ml heptadecafluorodecyltrimethoxysilane are put into a sealed container, and the surface fluorination treatment of the film is carried out at 60℃ for 20h to obtain the high light transmittance, low haze and super-hydrophobic SiO2film.

[0052] Example 6:

[0053] Dow Corning DC184 optical glue was mixed and stirred according to the main agent 1 g, the auxiliary agent 0.1 g to produce a large number of bubbles, then 10 ml of tetrahydrofuran was added, and ultrasonic treatment was performed for 10 min to obtain a Dow Corning DC184 solution.

[0054] The SiO2sol 15 ml (particle size distribution was 20 nm:40 nm=7.5 ml:7.5 ml), 15 ml of tetrahydrofuran, 0.1 ml of γ-mercaptopropyl triethoxysilane, and 0.4 ml of the Dow Corning DC184 solution were taken into a beaker, and stirring was performed at room temperature for 24 h to obtain a modified SiO2sol.

[0055] The dip-coating method was used to coat films on transparent organic glass (PMMA) and silicate glass, the pulling speed was 1200 μm / s, the pulling number was 4 times, the dipping time was 2 min, and the curing time was 24 h.

[0056] The substrate containing the film (the film area was 48 cm 2 , 6 cm x 8 cm) was placed in a sealed container together with 0.05 ml of tridecafluoro octyl trimethoxysilane, and the surface fluorination treatment of the film was performed at 80°C for 12 h to obtain a high-transmittance, low-haze, and super-hydrophobic SiO2film.

[0057] Example 7:

[0058] Dow Corning DC184 optical glue was mixed and stirred according to the main agent 2 g, the auxiliary agent 0.2 g to produce a large number of bubbles, then 10 ml of tetrahydrofuran was added, and ultrasonic treatment was performed for 10 min to obtain a Dow Corning DC184 solution.

[0059] The SiO2sol 15 ml (particle size distribution was 30 nm:40 nm=10 ml:5 ml), 15 ml of tetrahydrofuran, 0.1 ml of γ-mercaptopropyl triethoxysilane, and 0.4 ml of the Dow Corning DC184 solution were taken into a beaker, and stirring was performed at room temperature for 24 h to obtain a modified SiO2sol.

[0060] The dip-coating method was used to coat films on transparent organic glass (PMMA) and silicate glass, the pulling speed was 1200 μm / s, the pulling number was 4 times, the dipping time was 3 min, and the curing time was 32 h.

[0061] The substrate containing the film (the film area was 48 cm 2 , 6 cm x 8 cm) was placed in a sealed container together with 0.05 ml of dodecafluoroheptyl propyl trimethoxysilane, and the surface fluorination treatment of the film was performed at 80°C for 12 h to obtain a high-transmittance, low-haze, and super-hydrophobic SiO2film.

[0062] Table 1 Inorganic glass adhesion rating of SiO2containing film

[0063]

[0064] Table 2. Plexiglas Adhesion Rating of SiO2 Containing Films

[0065]

Claims

1. A method for preparing a high-transmittance, low-haze, super-hydrophobic SiO2 film, characterized in that, The method comprises the following steps: (1) adding tetraethyl orthosilicate into an ethanol solution containing deionized water and ammonia, and treating in a water bath at 40-70 DEG C for 4-12 h to obtain SiO2 sol, wherein the volume ratio of tetraethyl orthosilicate: ammonia: ethanol: deionized water is (3-12) ml: (1-4) ml: (40-110) ml: (2-8) ml; The particle size of SiO2 in the SiO2 sol is any two of 10 nm, 20 nm, 30 nm and 40 nm; (2) adding tetrahydrofuran, silane coupling agent and Dow Corning optical glue solution into the SiO2 sol respectively, and stirring at room temperature for 18-32 h to obtain modified SiO2 sol, wherein the silane coupling agent is selected from one of gamma-mercaptopropyl trimethoxysilane, gamma-mercaptopropyl triethoxysilane, gamma-glycidyl ether propyl trimethoxysilane and gamma-methacryloyloxy propyl trimethoxysilane, and the volume ratio of SiO2 sol: tetrahydrofuran: silane coupling agent: Dow Corning optical glue solution is (10-20):(10-20):(0.05-0.1):(0.4-0.6); The Dow Corning optical glue is composed of a main agent and a secondary agent, the main agent is polydimethylsiloxane, and the secondary agent is a crosslinking agent; the crosslinking agent is a mixture containing dimethyl methyl hydrogen, vinyl-terminated dimethyl polysiloxane, vinyl MQ resin mixture and tetramethyl tetra-vinyl cyclo tetra siloxane; after mixing the main agent with the secondary agent, tetrahydrofuran is added and ultrasonic dissolution is performed to obtain the Dow Corning optical glue solution; (3) ultrasonically treating the glass substrate in deionized water and ethanol solution for 1-2 min, and taking out and drying for standby use; the glass is inorganic glass or organic glass; (4) using the modified SiO2 sol to prepare a film by dip-coating method, the drawing speed is 500-2000 μm / s, the drawing times is 2-8, the dipping time is 1-3 min, and the film is cured at room temperature for 18-32 h after film formation; (5) placing the substrate containing the film and perfluoro silane in a sealed container, and evaporating the perfluoro silane to the surface of the film at a certain temperature to perform surface fluorination treatment, thereby obtaining the SiO2 film with high light transmittance, low haze and super-hydrophobicity.

2. The method of claim 1, wherein, In step (1), the particle size of SiO2 in the SiO2 sol is any two of 10 nm, 20 nm, 30 nm and 40 nm; The volume ratio of SiO2 sol with relatively small particle size: SiO2 sol with relatively large particle size is 17:3-1:

1.

3. The method of claim 1, wherein, In step (2), the type of the Dow Corning optical glue is DC184, and the volume ratio of main agent: secondary agent: tetrahydrofuran is (1-2) g: (0.1-0.4) g: (10-20) ml.

4. The method of claim 1, wherein, In step (5), the perfluoro silane is one of heptadecafluorodecyl trimethoxysilane, tridecafluorooctyl trimethoxysilane and dodecafluoroheptyl propyl trimethoxysilane.

5. The method of claim 1, wherein, Step (5) every 48 cm 2 The film area corresponds to the amount of perfluorosilane 0.05 ml, fluorination treatment temperature is 30-80℃, and the treatment time is 12-24h.

6. The SiO2 film is prepared by the method according to any one of claims 1-5.

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