A method for preparing a superhydrophobic and low refractive index antireflection film

Abstract

The present invention discloses a method for preparing a super-hydrophobic, low-refractive-index antireflection film, comprising: mixing polyacrylic acid, anhydrous ethanol, and aqueous ammonia to obtain a sol; adding a certain amount of ethyl orthosilicate to the obtained sol for a certain period of time for aging; adding a certain proportion of hexamethyldisilazane to the aged sol, stirring, and allowing to stand to obtain a sol A; performing plasma cleaning on a substrate using a plasma cleaning machine; and coating the obtained sol A on a substrate using a pulling coating machine at different pulling speeds and immersion times to obtain a super-hydrophobic, low-refractive-index antireflection film. The present invention uses polyacrylic acid as a raw material and, by controlling the immersion time and pulling speed of the sol, prepares an antireflection film having super-hydrophobicity and a low refractive index, providing a new method for further reducing the refractive index of other thin films.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical film materials, and more specifically, relates to a method for preparing a super-hydrophobic, low-refractive-index anti-reflection film. Background Art

[0002] In optical science, the refractive index of a medium is considered one of the most important physical quantities. This is because the refractive index of a medium not only controls the phase velocity of light, but also has a significant impact on the refraction, reflection, and diffraction of light at the boundaries of the medium. To date, a lot of research has been conducted on the theory of broadband antireflection coatings with different refractive index linearity, especially when the surrounding environment is air. The refractive index n1 of an ideal antireflection coating must comply with the following two conditions: 1. n1 = (n 0* n s ) 1 / 2 , where n0 and n s where d is the refractive index of air and the substrate, respectively; 2.d = λ / 4n1, where d is the film thickness and λ is the wavelength of the incident light. Therefore, for a given substrate, an ideal single-layer antireflection coating has limitations in terms of both film refractive index and thickness, particularly in terms of refractive index. For example, for a BK7 glass substrate with a refractive index of 1.5151 (633 nm), the formula for calculating the refractive index of a single-layer film indicates a refractive index of approximately 1.22. However, materials with such a low refractive index are not commonly found in nature. Ultra-low refractive index materials are required in numerous fields, such as omnidirectional reflectors, distributed Bragg reflectors, optical microresonators, and light-emitting diodes. Therefore, further lowering the refractive index of materials is necessary to meet these application requirements. Due to the relationship between refractive index and porosity, an effective method for lowering the refractive index is to introduce voids into the material. Therefore, porous SiO2-based films are attractive materials for antireflection coatings due to their high specific surface area, low dielectric constant, and easily tunable refractive index. Consequently, extensive research has been conducted on the preparation of low-refractive-index materials. Physical vapor deposition and chemical etching are the two simplest technologies and are currently the most commonly used methods. However, this preparation method is very expensive and not very convenient to control the refractive index and film thickness of the film, and is not suitable for operation on large substrates. Mesoporous SiO2 can also be used to prepare porous films with low refractive index and high transparency. However, the high-temperature calcination used is extremely unfavorable for some polymer substrates and will produce stress on the glass substrate. The film prepared by nano-etching mesoporous SiO2 with hydrofluoric acid solution requires the use of toxic and harmful etchants, which is extremely unfavorable for large-scale production. Therefore, a method for preparing porous materials under mild conditions is extremely urgent. Summary of the Invention

[0003] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0004] In order to achieve these objects and other advantages according to the present invention, a method for preparing a super-hydrophobic, low-refractive-index antireflection film is provided, comprising:

[0005] Step 1: Mixing polyacrylic acid, anhydrous ethanol and ammonia water to obtain a sol;

[0006] Step 2: adding a certain amount of ethyl orthosilicate to the sol obtained in step 1 for a certain period of time for aging;

[0007] Step 3: adding a certain proportion of hexamethyldisilazane to the aged sol, stirring, and allowing to stand to obtain sol A;

[0008] Step 4: Use a plasma cleaning machine to perform plasma cleaning on the substrate;

[0009] Step 5: Using a pulling coating machine, using different pulling speeds and immersion times, the sol A obtained in step 3 is coated on the substrate to obtain a super-hydrophobic, low-refractive-index anti-reflection film.

[0010] Preferably, in step 1, the mass volume ratio of polyacrylic acid, anhydrous ethanol and ammonia water is 0.5-0.9 g:120-160 mL:5-10 mL.

[0011] Preferably, in the step 1, the stirring temperature is 25-35° C. and the stirring time is 7 h.

[0012] Preferably, in the step 2, the tetraethyl orthosilicate is added in five times, the time interval between additions is 1 hour, and the mass volume ratio of polyacrylic acid to the tetraethyl orthosilicate added in each time is 0.5-0.9 g:1 mL.

[0013] Preferably, in the step three, the volume mass ratio of hexamethyldisilazane to the polyacrylic acid in the step one is 3-8 mL:0.5-0.9 g, the stirring time is 20-40 min, and the standing time is 24 h.

[0014] Preferably, in step 4, the plasma cleaning machine is PCE-6, the cleaning power is 10 to 60 W, and the cleaning time is 2 to 10 minutes.

[0015] Preferably, in the step five, the SiO2 film is plated using a pulling coating machine at the same pulling speed and with an immersion time of 0.1 to 15 minutes.

[0016] Preferably, in the step five, the SiO2 film is deposited using a pulling coating machine at a pulling speed of 20 to 200 mm / min under the same immersion time.

[0017] Preferably, the surface of the super-hydrophobic, low-refractive-index anti-reflection film is further coated with a surface film, and the preparation method of the surface film includes:

[0018] S1. Performing transparency-enhancing modification on polyacrylic acid to obtain modified polyacrylic acid. The specific method includes:

[0019] Adding polyacrylic acid to deionized water, stirring and dissolving at a temperature of 30 to 50° C., and allowing to stand to obtain a polyacrylic acid solution; adding sorbitol powder to the polyacrylic acid solution, heating the temperature to 60 to 90° C. at a heating rate of 2 to 6° C. / min, continuously stirring the solution at a stirring rate of 100 to 300 rpm during the heating process, maintaining the temperature for 1 to 3 hours, and then evaporating, concentrating, and drying to obtain a modified polyacrylic acid solid;

[0020] S2. Sol B is prepared using butyl titanate and modified polyacrylic acid. The specific method includes:

[0021] Butyl titanate and modified polyacrylic acid were mixed in a certain mass ratio, then added into anhydrous ethanol and stirred evenly to obtain a mixed solution; deionized water was slowly added into the mixed solution while stirring for 20 to 40 minutes, and finally ammonia water was added, stirred and allowed to stand for 2 to 6 hours to obtain sol B.

[0022] S3. Pulling and coating sol B on the surface of the antireflection film coated with sol A. The specific method includes: immersing the substrate coated with sol A into sol B, coating at a pulling speed of 80 to 120 mm / min to obtain a surface film, thereby preparing an antireflection film with an A / B structure.

[0023] Preferably, in said S1, the mass volume ratio of polyacrylic acid, sorbitol and deionized water is 10-20 g: 2-5 g: 120-300 mL;

[0024] In S2, the mass volume ratio of butyl titanate, modified polyacrylic acid, anhydrous ethanol, deionized water, and ammonia water is 0.6-1.0 g: 0.4-0.8 g: 100-160 mL: 60-80 mL: 8-12 mL.

[0025] The present invention has at least the following beneficial effects: the present invention uses polyacrylic acid as a main raw material and prepares an antireflection film with super-hydrophobicity and low refractive properties through a sol-gel method.

[0026] At the same time, the present invention uses sorbitol to perform anti-reflection modification on polyacrylic acid, thereby improving the light transmittance of polyacrylic acid, and after mixing with butyl titanate, it is plated on the surface of sol B to obtain an A / B double-layer anti-reflection film, further reducing the refractive index of the anti-reflection film.

[0027] The present invention uses a Czochralski coating machine to coat SiO2 thin films on substrates using different pulling speeds and immersion times, producing a series of SiO2 films whose refractive index changes with pulling speed and immersion time. By summarizing the variation patterns, it was concluded that by extending the Czochralski immersion time and increasing the pulling speed, the refractive index and reflectivity of the films can be further reduced, while the transmittance and thickness of the films can be increased. The refractive index of this series of antireflection films can be reduced to a minimum of 1.192, with a maximum transmittance of 99% and a minimum reflectance of 0.5%. This method regulates the optical parameters of sol-gel films prepared by the Czochralski method, such as film thickness, refractive index, and transmittance, without changing the properties of the raw materials or the sol, providing a new approach for further reducing the refractive index of other films.

[0028] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Graphs showing the transmittance of antireflection films prepared in Examples 1 to 7 and 12 of the present invention;

[0030] Figure 2 Graphs showing changes in film thickness and refractive index for the antireflection films prepared in Examples 1 to 7 of the present invention; Figure 3 The water contact angle diagram of the antireflection film prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0032] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0033] Example 1

[0034] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index anti-reflection film, comprising the following steps:

[0035] Step 1: Take 0.7 g of polyacrylic acid, 140 mL of anhydrous ethanol, and 7 mL of ammonia water, mix the above three solutions in a sealed two-necked flask, and magnetically stir at 30°C for 7 hours.

[0036] Step 2: While the above solution is being stirred, 1 ml of ethyl orthosilicate is added every 1 h for a total of 5 times, and the solution is aged for 48 h after stirring.

[0037] Step 3: Add 5.5 mL of hexamethyldisilazane to the aged sol and stir for 30 minutes, then let it stand for 24 hours.

[0038] Step 4: Use a PCE-6 plasma cleaning machine to perform plasma cleaning on the substrate with a cleaning power of 30W and a cleaning time of 5 minutes.

[0039] Step 5: Use a pulling coating machine to coat the SiO2 film at a pulling speed of 200 mm / min and an immersion time of 0.1 min. The film thickness is 244.5 nm.

[0040] Example 2

[0041] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index antireflection film. The difference from Example 1 is that the pulling speed in step five is 20 mm / min, and the remaining steps are the same as Example 1. The film thickness deposited in this embodiment is 90.6 nm.

[0042] Example 3

[0043] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index antireflection film. The difference from Example 1 is that the pulling speed in step five is 50 mm / min, and the remaining steps are the same as Example 1. The film thickness deposited in this embodiment is 117.3 nm.

[0044] Example 4

[0045] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index antireflection film. The difference from Example 1 is that the pulling speed in step five is 80 mm / min, and the remaining steps are the same as Example 1. The film thickness deposited in this embodiment is 137.2 nm.

[0046] Example 5

[0047] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index antireflection film. The difference from Example 1 is that the pulling speed in step 5 is 120 mm / min, and the remaining steps are the same as in Example 1. The film thickness of this embodiment is 187.7 nm.

[0048] Example 6

[0049] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index antireflection film. The difference from Example 1 is that the pulling speed in step five is 150 mm / min, and the remaining steps are the same as Example 1. The film thickness deposited in this embodiment is 224.5 nm.

[0050] Example 7

[0051] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index antireflection film. The difference from Example 1 is that the pulling speed in step five is 180 mm / min, and the remaining steps are the same as Example 1. The film thickness deposited in this embodiment is 231.4 nm.

[0052] Example 8

[0053] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index antireflection film. The difference from Example 1 is that the immersion time in step five is 1 minute, and the remaining steps are the same as those in Example 1.

[0054] Example 9

[0055] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index antireflection film. The difference from Example 1 is that the immersion time in step five is 5 minutes, and the remaining steps are the same as those in Example 1.

[0056] Example 10

[0057] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index antireflection film. The difference from Example 1 is that the immersion time in step five is 10 minutes, and the remaining steps are the same as those in Example 1.

[0058] Example 11

[0059] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index antireflection film. The difference from Example 1 is that the immersion time in step five is 15 minutes, and the remaining steps are the same as those in Example 1.

[0060] Example 12

[0061] This embodiment provides a method for preparing a super-hydrophobic, low-refractive-index antireflection film. The difference from Example 1 is that in this embodiment, a layer of sol B is deposited on the surface of sol A by pulling and coating, and a surface film is deposited on the surface of sol A, thereby obtaining a double-layer antireflection film with an A / B structure. The method for obtaining the surface film by pulling and coating sol B includes:

[0062] S1. Performing transparency-enhancing modification on polyacrylic acid to obtain modified polyacrylic acid. The specific method includes:

[0063] 15 g of polyacrylic acid was added to 250 mL of deionized water, stirred and dissolved at 50° C., and allowed to stand to obtain a polyacrylic acid solution; 5 g of sorbitol powder was added to the polyacrylic acid solution, and the temperature was increased to 80° C. at a heating rate of 2° C. / min. Stirring was continued during the heating process at a stirring rate of 150 rpm. After maintaining the temperature for 1 hour, the solution was evaporated, concentrated, and dried to obtain a modified polyacrylic acid solid;

[0064] S2. Sol B is prepared using butyl titanate and modified polyacrylic acid. The specific method includes:

[0065] 1.0 g of butyl titanate and 0.8 g of modified polyacrylic acid were mixed, then added to 150 mL of anhydrous ethanol and stirred to obtain a mixed solution; 60 mL of deionized water was slowly added to the mixed solution, and stirred for 40 min. Finally, 8 mL of ammonia water was added, stirred, and allowed to stand for 5 h to obtain Sol B.

[0066] S3. Pulling and coating sol B on the surface of the antireflection film coated with sol A. The specific method includes: immersing the substrate coated with sol A into sol B, coating at a pulling speed of 100 mm / min to obtain a surface film, thereby preparing an antireflection film with an A / B double-layer structure.

[0067] The transmittance and refractive index of the antireflection films prepared in Examples 1 to 7 and 12 were measured respectively, and the results were as follows: Figure 1 and Figure 2 ,from Figure 1 and Figure 2 It can be seen that the antireflection film prepared in Example 1 has a refractive index of 1.192 and a transmittance of up to 99% as measured by UV spectrophotometer and ellipsometry. The antireflection film of A / B double-layer structure prepared by mixing modified polyacrylic acid and butyl titanate in Example 12 has a refractive index of 1.065, indicating that the refractive index of the antireflection film prepared in Example 1 is significantly better than that of the antireflection film prepared in Example 1, and the transmittance of the antireflection film prepared in Example 12 is also significantly better than that of Example 1. At the same time, the water contact angle of the antireflection film prepared in Example 1 is measured, as shown in FIG. Figure 3 At any time, the water contact angle is 155°, indicating that the antireflection film prepared in Example 1 has superhydrophobicity.

[0068] The number of devices and processing scales described herein are intended to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be readily apparent to those skilled in the art.

[0069] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a super-hydrophobic, low-refractive-index antireflection film, characterized in that: The following steps are involved: Step 1: Mixing polyacrylic acid, anhydrous ethanol and ammonia water to obtain a sol; Step 2: adding a certain amount of ethyl orthosilicate to the sol obtained in step 1 for a certain period of time for aging; Step 3: adding a certain proportion of hexamethyldisilazane to the aged sol, stirring, and allowing to stand to obtain sol A; Step 4: Use a plasma cleaning machine to perform plasma cleaning on the substrate; Step 5: Using a pulling coating machine, using different pulling speeds and immersion times, the sol A obtained in step 3 is coated on the substrate to obtain a super-hydrophobic, low-refractive-index anti-reflection film; The surface of the super-hydrophobic, low-refractive-index anti-reflection film is further provided with a surface film, and the preparation method of the surface film comprises: S1. Performing transparency-enhancing modification on polyacrylic acid to obtain modified polyacrylic acid. The specific method includes: Add polyacrylic acid to deionized water, stir and dissolve at 30-50°C, and allow to stand to obtain a polyacrylic acid solution; add sorbitol powder to the polyacrylic acid solution, heat it to 60-90°C at a heating rate of 2-6°C / min, continue stirring during the heating process at a stirring rate of 100-300 rpm, maintain the temperature for 1-3 hours, and then evaporate, concentrate, and dry to obtain a modified polyacrylic acid solid; the mass volume ratio of polyacrylic acid, sorbitol, and deionized water is 10-20g:2-5g:120-300mL; S2. Sol B is prepared using butyl titanate and modified polyacrylic acid. The specific method includes: Butyl titanate and modified polyacrylic acid are mixed in a certain mass ratio, then added to anhydrous ethanol and stirred to obtain a mixed solution; deionized water is slowly added to the mixed solution while stirring for 20-40 minutes, and finally ammonia water is added, stirred, and allowed to stand for 2-6 hours to obtain Sol B; the mass volume ratio of butyl titanate, modified polyacrylic acid, anhydrous ethanol, deionized water, and ammonia water is 0.6-1.0 g:0.4-0.8 g:100-160 mL:60-80 mL:8-12 mL; S3. Pulling and coating sol B on the surface of the antireflection film coated with sol A. The specific method includes: immersing the substrate coated with sol A into sol B, coating at a pulling speed of 80-120 mm / min to obtain a surface film, thereby preparing an antireflection film with an A / B structure.

2. The method for preparing a super-hydrophobic, low-refractive-index antireflection film according to claim 1, wherein: In the step 1, the mass volume ratio of polyacrylic acid, anhydrous ethanol, and ammonia water is 0.5-0.9 g: 120-160 mL: 5-10 mL.

3. The method for preparing a super-hydrophobic, low-refractive-index antireflection film according to claim 1, wherein: In the step 1, the stirring temperature is 25-35° C. and the stirring time is 7 h.

4. The method for preparing a super-hydrophobic, low-refractive-index antireflection film according to claim 1, wherein: In the step 2, the tetraethyl orthosilicate is added in five times, the time interval between additions is 1 hour, and the mass volume ratio of polyacrylic acid to tetraethyl orthosilicate added in each time is 0.5-0.9 g:1 mL.

5. The method for preparing a super-hydrophobic, low-refractive-index antireflection film according to claim 1, wherein: In the step 3, the volume mass ratio of hexamethyldisilazane to the polyacrylic acid in the step 1 is 3-8 mL: 0.5-0.9 g, the stirring time is 20-40 min, and the standing time is 24 h.

6. The method for preparing a super-hydrophobic, low-refractive-index antireflection film according to claim 1, wherein: In step 4, the plasma cleaning machine is PCE-6, the cleaning power is 10-60W, and the cleaning time is 2-10 minutes.

7. The method for preparing a super-hydrophobic, low-refractive-index antireflection film according to claim 1, wherein: In the step 5, the SiO2 film is plated using a pulling coating machine at the same pulling speed and according to an immersion time of 0.1 to 15 minutes.

8. The method for preparing a super-hydrophobic, low-refractive-index antireflection film according to claim 1, wherein: In the step 5, the SiO2 film is deposited using a pulling coating machine at a pulling speed of 20-200 mm / min under the same immersion time.

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