KR101259078B1 - Method for fabricating superhydrophobic thin film - Google Patents

Abstract

The present invention relates to a manufacturing method for manufacturing a super water-repellent TiO ₂ thin film on a glass substrate by a wet process method, in order to prepare a thin film having a rough surface of a micro-nano composite structure layer-by-layer (LBL) deposition Method and liquid phase deposition (LPD) method were used. The super water repellent thin film is prepared by preparing a (PAH / PAA) thin film having a texture structure by the LBL method, then laminating TiO ₂ nanoparticles by the LPD method, and water repelling the surface using fluoroalkyltrimethoxysilane (FAS). It was. (PAH / PAA) _{10 The} thin film of TiO ₂ laminated on the surface of the thin film for 45 minutes showed a rough surface with RMS roughness of 65.6 nm. It showed over 80% transmittance. Surface structures, optical properties, and contact angles of thin films prepared under different conditions were measured using FE-SEM, AFM, UV-Vis, and contact angel meters.

Super water-repellent, LPD method, LBL method, FAS

Description

Super water-repellent thin film manufacturing method {METHOD FOR FABRICATING SUPERHYDROPHOBIC THIN FILM}

The present invention relates to a method for producing a super water-repellent TiO ₂ thin film on a glass substrate by a wet process method.

 Super water-repellent self-cleaning thin films having a water contact angle of 150 ° or more have been reported to be applied to building exterior materials, chemical and bio-sensors, displays, automobile glass, and solar cell module glass which have excellent pollution resistance. In order to manufacture a super water-repellent thin film, a process of first forming a rough surface having an uneven structure on the surface of the substrate and a process of modifying the surface using a compound having a low surface energy is used.

The present invention aims to produce a super water-repellent thin film using the LBL method and the LPD method in order to produce a high surface roughness of the micro-nano composite structure.

In order to achieve the above object, the present invention provides a method of manufacturing a super water-repellent thin film by laminating TiO ₂ nanoparticles on the (PAH / PAA) thin film and then FAS treating the surface thereof.

In addition, the present invention after the (PAH / PAA) thin film production by the LBL method and the TiO ₂ by LPD method thereon The present invention provides a method of manufacturing a super water-repellent thin film by laminating nanoparticles and treating the surface thereof.

And, the present invention can form a super water-repellent thin film through the above manufacturing method.

The present invention can produce a thin film having a super water-repellent property, and the thin film produced thereby has the effect of having a high transmittance.

BRIEF DESCRIPTION OF THE DRAWINGS The above objects, features and advantages will become more apparent through the following examples in conjunction with the accompanying drawings. Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Super water-repellent self-cleaning thin films having a water contact angle of 150 ° or more have been reported to be applied to building exterior materials, chemical and bio-sensors, displays, automobile glass, solar cell module glass, which have excellent pollution resistance, and many studies on thin film manufacturing have been reported. In order to manufacture a super water-repellent thin film, a process of first forming a rough surface having an uneven structure on the surface of the substrate and a process of modifying the surface using a compound having a low surface energy is used. Typical self-cleaning glass is manufactured by coating TiO ₂ having a photocatalyst, anti-fogging, and anti-bacterial properties on a glass substrate. TiO ₂ thin films are manufactured by various methods such as sol-gel, sputtering, chemical vapor deposition (CVD), layer-by-layer (LBL), and liquid phase deposition (LPD). In particular, the LBL method and the LPD method, which are wet processes, have a simple thin film manufacturing process, are easy to control the film thickness on a nano scale, and have advantages in large area coating. The LBL method is a technique of manufacturing a thin film using electrostatic forces of materials having different charges by alternately depositing a substrate in an electrolyte polymer solution or a nanoparticle dispersion solution having a positive or negative charge dissolved or dispersed in water at room temperature and normal pressure. LBL method can produce a thin film having a surface of various structures by controlling the concentration, pH, deposition time, etc. of the electrolyte solution. In the preparation of TiO ₂ thin film by LPD method, the precursors (TiF ₄ , TiCl ₄ ) are dissolved in water, the concentration and pH of the solution are titrated, and the substrate is immersed in an aqueous solution to maintain a temperature of about 60 to 70 ° C. according to the deposition time. It is a technique of coating a film on a substrate by controlling the thickness and growth rate of. These methods can be said to be suitable methods for forming an uneven structure film on a substrate.

In order to hydrophobically modify the surface of the uneven structure, fluorine or silicon compounds are widely used, and among them, fluoroalkyltrimethoxysilane (FAS, CF ₃ (CF ₂ ) ₇ CH ₂ CH, which has very low surface energy (~ 8mJ / m ² ) ₂ Si (OCH ₃ ) ₃ ,) is widely used. In addition, in the present invention, in order to prepare a thin film having a high surface roughness of the micro-nano composite structure, the surface and optical properties of the film were confirmed by the experimental conditions using the LBL method and the LPD method, and the thin film manufactured by the water repellent treatment using the FAS. The surface contact angle of was confirmed.

Poly (allylamine hydrochloride) with positive charge (PAH, Aldrich, Mw = 70,000g) and poly (acrylic acid) with negative charge (PAA, Aldrich, Mw = 100,000, 35) wt.% solution in water) was used. The concentration of the two electrolyte polymers used was 0.01M, and the pH of the solution was titrated to pH9.5 and pH6.0 using NaOH, respectively. Titanium (IV) fluoride (TiF ₄ , Aldrich) was used to prepare the TiO ₂ thin film by LPD method. The concentration of the solution was adjusted to pH 2.0 using 0.04M, pH using NH ₄ OH. The slide glass was used as a substrate, and distilled water and ethanol were mixed at a volume ratio of 2: 3, and the substrate was immersed in a solution containing 1.0 wt.% KOH, followed by ultrasonic treatment for 5 to 10 minutes, followed by distilled water. It was washed using. The hydrophilized substrate was first immersed in PAH solution for 10 minutes and then immersed in distilled water three times for 1 minute and washed. Subsequently, it was immersed in a PAA solution for 10 minutes and then washed three times with distilled water for 1 minute. This process was repeated 5, 10, 15 times with 1 bilayer. After that, when 5 bilayers are stacked, (PAH / PAA) ₅ is indicated. The glass substrate on which the polymer film was deposited by the LBL method was deposited in a TiF ₄ solution for 30 minutes, 45 minutes, 1 hour, and 2 hours and maintained at 70 ° C. Thereafter, the substrate was washed with distilled water, and the substrate was dipped in 2 wt.% FAS solution diluted in hexane solution for 20 minutes for water repellent treatment, and then dried at 100 ° C. for one hour. A thin film manufacturing schematic is shown in FIG.

A field emission scanning electron microscope (FE-SEM, JSM 6700, JEOL) was used to confirm the surface microstructure of the prepared thin film, and a UV-Vis spectrophotometer (V-570, JASCO) was used to analyze the optical properties of the thin film. The transmittance was measured. The surface roughness of the thin film was measured using an atomic force microscope (AFM, JSPM5200, JEOL, Japan), and a contact angle meter (Easy Drop, KRUSS) was used to confirm the water contact angle of the prepared thin film surface.

The microstructure according to the number of bilayers of the (PAH / PAA) thin film coated on the glass substrate by the LBL method is shown in FIG. 2. The (PAH / PAA) ₅ thin film does not yet have a texture structure, and the (PAH / PAA) ₁₀ thin film has a texture structure. As the number of bilayers was increased from 5 to 15, the size of the texture structure was confirmed to increase. The transmittance of the prepared (PAH / PAA) _5,10,15 thin film is shown in FIG. 3. Having a flat surface (PAH / PAA) ₅ thin film on a glass substrate and showed almost the same transmittance (PAH / PAA) _10,15 thin film has been slightly lowered transmittance due to the formation of the texture structure or more than 89% in wavelength 550 nm High transmittance was shown. FIG. 4 shows the microstructure of a thin film on which TiO ₂ was formed by immersing a glass substrate and a glass substrate coated with 5, 10, and 15 bilayers (PAH / PAA) thin films in an LPD solution for 45 minutes. Glass substrates not coated with (PAH / PAA) form TiO ₂ clusters on the order of 200 – 300 nm, but are quite small. In comparison, much more TiO ₂ was formed on the surface of the (PAH / PAA) ₅ thin film.

It can be seen that TiO ₂ nanoparticles are densely formed on the surface of the (PAH / PAA) _10,15 thin film having a textured structure. FIG. 5 shows the time-dependent microstructure of the LPD method for forming a TiO ₂ film on the surface of a (PAH / PAA) ₁₀ thin film. As can be seen from the figure, the TiO ₂ nanoparticles are densely formed on the surface of the (PAH / PAA) thin film and almost 60 (PAH / PAA) after 60 minutes due to the increase in the thickness of the TiO ₂ thin film as the solution deposition time increases. The texture structure is not visible. Furthermore, after 120 minutes of deposition, cracks occurred on the surface of the thin film. FIG. 8 shows the water contact angle of the thin film prepared according to the number of bilayers of the (PAH / PAA) thin film and the deposition time of the LPD method using the FAS. A thin film of TiO ₂ formed on the surface by depositing (PAH / PAAA) _5,10,15 thin film deposited on a glass substrate for 45 minutes showed a super water-repellent property with a contact angle of 150 ° or more.

As the stacking time increased from 30 minutes to 45 minutes, the contact angle increased by 5-10 °, and when it increased from 60 minutes to 120 minutes, the contact angle gradually decreased. As shown in FIG. 5, TiO ₂ was formed on the surface of the polymer (PAH / PAA) thin film until 45 minutes to form a micro-nano composite structure, but after 45 minutes, the texture structure disappeared and the surface roughness was reduced. Because. 6 shows the transmittance of a thin film prepared over time after (PAH / PAA) ₁₀ thin film was deposited in a TiF ₄ solution. As the deposition time increases, the film thickness of TiO ₂ increases, so that the transmittance is lowered. Among the samples prepared under different conditions, the film deposited with TiO ₂ on the surface of (PAH / PAA) ₁₀ thin film for 45 minutes showed super water-repellent thin film having a transmittance of 80% or more and a contact angle of 155 ° after the wavelength of 650 nm. FIG. 7 is an AFM image of a thin film prepared by depositing TiO ₂ on a surface of a (PAH / PAA) ₁₀ thin film for 45 minutes, and a contact angle image of water. The root mean square (RMS) surface roughness of this film was measured at 65.6 nm.

After preparing a thin film having a rough surface of the micro-nano composite structure by using the LBL method and LPD method, a super water-repellent thin film was prepared by water repellent treatment of the surface of the thin film prepared by using FAS. The (PAH / PAA) film laminated with PAH of pH9.0 and PAA of pH6.0 showed a flat surface structure when the number of bilayers was 5, but increased to 10 and 15 to form the surface of the texture structure. These films showed high transmittance in the visible region. TiO ₂ nanoparticles formed by LPD method showed more active grain growth on the surface of (PAH / PAA) thin film coated on glass substrate. As the deposition time increased to 60 minutes and 120 minutes in excess of 45 minutes, the texture structure of (PAH / PAA) could not be confirmed due to the growth of the TiO ₂ film. Particularly, the thin film in which TiO ₂ was laminated on the surface of (PAH / PAA) ₁₀ thin film for 45 minutes showed a rough surface with RMS roughness of 65.6 nm, and after the water repellent treatment, the contact angle improved to 155 ° and 80% at wavelength above 650 nm. The above transmittance was shown.

Table 1 below shows the number of bilayers of the (PAH / PAA) thin film and the contact angle of the TiO ₂ thin film prepared according to the deposition time of the LPD method.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Will be clear to those who have knowledge of.

1 is a schematic diagram for manufacturing a super water-repellent thin film.

2 is an FE-SEM image according to the number of Bilayers of a (PAH / PAA) n thin film coated on a glass substrate.

3 is a transmission spectrum according to the number of Bilayers of a (PAH / PAA) n thin film coated on a glass substrate.

4 is a TiO ₂ formed by depositing a glass substrate coated with a glass substrate of 5, 10, 15 bilayers (PAH / PAA) thin film in LPD solution for 45 minutes. SEM image of the thin film.

5 is prepared TiO ₂ on the surface of the (PAH / PAA) ₁₀ thin film according to the deposition time SEM image of the thin film.

6 shows TiO ₂ prepared on the surface of (PAH / PAA) ₁₀ thin film according to deposition time. The transmittance spectrum of the thin film.

7 is an AFM image of a TiO ₂ thin film with water droplets on the surface image of a TiO ₂ thin film been produced on the surface of (PAH / PAA) ₁₀ having a thin film deposition time of 45 minutes.

8 is a view showing a transparent super water-repellent superhydrophilic patterning process.

9 is a view showing a manufacturing process of the TiO ₂ thin film using the LBL-SA method and LPD method.

Claims (9)

(PAH / PAA) thin film is formed on the substrate through LBL method The TiO ₂ nanoparticles were laminated for 45 minutes on the top of the (PAH / PAA) thin film by LPD method, and the laminated surface was subjected to FAS treatment. The (PAH / PAA) thin film is manufactured by repeating the process of hydrophilic treatment of the substrate and then immersing the hydrophilized substrate in PAH having a positive charge, and soaking in a PAA having a negative charge and then cleaning the substrate 10 times. Method for producing a super water-repellent thin film. The method of claim 1, The substrate is Distilled water and ethanol were mixed in a volume ratio of 2: 3, immersed in a solution added with KOH, washed with distilled water and hydrophilized Method for producing a super water-repellent thin film. delete The method of claim 1, TiO ₂ Nanoparticles, The (PAH / PAA) thin film was immersed in TiF ₄ solution Method for producing a super water-repellent thin film. The method of claim 4 wherein the TiF ₄ solution is Indicating 0.04M concentration and PH 2.0 Method for producing a super water-repellent thin film. delete The method of claim 1, The FAS process, The TiO ₂ The substrate on which the nanoparticles are stacked is washed with distilled water, dipped in FAS solution diluted in hexane solution and dried Method for producing a super water-repellent thin film. The method of claim 1, further comprising a water repellent process after the FAS treatment. Method for producing a super water-repellent thin film. A super water-repellent thin film prepared by the method of any one of claims 1, 2, 4, 5, 7, and 8.

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