KR20150090333A - Super-hydrophobic PTFE Thin Films deposited on substrates and Manufacturing method thereof - Google Patents

Abstract

The present invention relates to a super-hydrophobic PTFE thin film comprising: a substrate whose surface is treated to form a fine structure on an upper surface; a buffer layer of a SiO_2 material deposited on the upper surface of the substrate; and a PTFE thin film layer deposited on the upper surface of the buffer layer. Moreover, the buffer layer and the PTFE thin film layer are deposited by a high frequency magnetron sputtering method respectively. According to the present invention, a buffer layer of the SiO_2 material is formed before the PTFE thin film layer deposited on a substrate whose surface is treated. Therefore, the present invention has an effect of increasing water repellency of a thin film by preventing the PTFE thin film layer, which is non-stick and has a low surface energy, from being separated from the substrate.

Description

TECHNICAL FIELD [0001] The present invention relates to a super-hydrophobic PTFE thin film deposited on a substrate, and a super-

The present invention provides a super-water-repellent PTFE thin film deposited on a substrate and a method of manufacturing the same, and more particularly, to a super-water-repellent PTFE thin film deposited on a substrate using a high frequency magnetron sputtering method capable of depositing a stable thin film on a large- And a method of manufacturing the PTFE thin film deposited on a substrate, which is capable of remarkably improving the super water repellency of the PTFE thin film by preventing the deposited PTFE thin film from peeling off from the substrate.

Recently, there has been a growing interest in ultra-water-repellent thin films having a contact angle of 150 ° or more due to the need for waterproofing and stain resistance to maintain their performance in architectural exterior materials, chemical and biosensors, displays, and automobile glasses.

It is known that the superfluidity of the thin film is affected by the low surface energy of the thin film material. Recently, PTFE material, which is well known as Teflon, has been attracting attention as such super water repellent material.

In general, the PTFE thin film is composed of carbon and fluorine and is widely used as an antifouling and water repellent coating material because it has excellent mechanical strength and thermal / chemical stability as well as excellent insulating property. , The deposition conditions and the surface condition of the substrate.

In particular, the PTFE thin film has a disadvantage in that it requires a variety of surface treatments for the substrate to be adhered due to poor adhesion to the substrate due to its low surface energy. In recent years, the characteristics of the deposited thin film have been stable, A method of depositing a PTFE thin film on a substrate using a high frequency magnetron sputtering method capable of increasing the adhesion between the deposited thin film and the substrate has been proposed.

The method of depositing the PTFE thin film using the high-frequency magnetron sputtering method is disclosed in detail in the following [1] published by the inventors of the present invention and the like.

However, even when the PTFE thin film is deposited using the high frequency magnetron sputtering method, the super water repellency is maintained at the initial stage of the deposition, but the water repellency is deteriorated due to the peeling of the PTFE thin film with time There is a desperate need for a solution to this problem.

[Reference 1] "Study on super-water repellency of PTFE thin film deposited on Al substrate using high frequency magnetron sputtering method", Journal of the Institute of Electrical and Electronic Material Engineers, Vol.24 No. 1, pp.64 ~ 69 )

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art described above, and it is an object of the present invention to provide a PTFE thin film which exhibits super water repellency due to low surface energy, The present invention provides a super-water-repellent PTFE thin film deposited on a substrate capable of further improving super-water repellency of the PTFE thin film and a method of manufacturing the same.

In order to achieve the above object, a super-water-repellent PTFE thin film deposited on a substrate according to the present invention comprises a substrate surface-processed to form a microstructure on an upper surface thereof, a buffer layer of SiO ₂ material deposited on an upper surface of the substrate, Wherein the buffer layer and the PTFE thin film layer are each deposited by a high frequency magnetron sputtering method.

The substrate is an aluminum substrate, and the surface treatment is performed by wet etching using dilute hydrochloric acid.

Further, the substrate is a glass substrate, and the surface treatment is performed by plasma etching using O ₂ gas.

Further, in the second water-repellent PTFE thin SiO ₂ material with an upper surface of the substrate a first step, the manufacturing method is surface-treated to form a microstructure on an upper surface of a substrate of a metallic material or a glass material for depositing on a substrate according to the invention A second step of depositing a buffer layer and a third step of depositing a PTFE thin film layer on the upper surface of the buffer layer, wherein the buffer layer and the PTFE thin film layer are deposited by a high frequency magnetron sputtering method in the second and third steps, respectively .

As described above in detail, the super-water-repellent PTFE thin film deposited on the substrate according to the present invention forms a PTFE thin film on a substrate using a high-frequency magnetron sputtering method. Therefore, when compared with the conventional chemical vapor deposition method or other physical vapor deposition methods, There is an advantage that a stable thin film can be formed in a large area.

In addition, since the super-water-repellent PTFE thin film deposited on the substrate according to the present invention is a method of surface-treating the upper surface of the substrate to form a microstructure before depositing the thin film on the substrate, the micropores And a superficial water repellency of about 150 DEG due to the low surface energy of the PTFE thin film.

Further, since the super-water-repellent PTFE thin film deposited on the substrate according to the present invention forms a buffer layer of SiO ₂ material before the PTFE thin film is deposited on the surface-treated substrate, the PTFE thin film having non- It is possible to prevent the phenomenon of peeling from the substrate and to further increase the water repellency of the thin film.

FIG. 1 is a view illustrating the structure of a substrate on which a super-water-repellent PTFE thin film deposited on a substrate according to a first embodiment of the present invention is formed,
FIG. 2 is a process flow diagram illustrating a method for depositing the super-water-repellent PTFE thin film shown in FIG. 1 on a substrate,
3 is a view showing the shape of a PTFE target manufactured according to the first embodiment of the present invention,
FIG. 4 is a graph showing a change in the contact angle according to the deposition time of the thin film manufactured according to the first embodiment of the present invention,
5 is a view for explaining a method of measuring a contact angle applied in the experiment of FIG. 4,
6 is a SEM surface image of a PTFE thin film according to a deposition time of a thin film manufactured according to the first embodiment of the present invention,
FIGS. 7 and 8 are graphs showing a comparison of the C1s XPS spectra of the substrate with and without PTFE deposited according to the first embodiment of the present invention,
9 is a graph showing changes in the contact angle according to the deposition time of a thin film manufactured according to the first embodiment of the present invention,
FIG. 10 is a graph showing super water-repellency characteristics of a PTFE thin film deposited according to the first embodiment of the present invention, and FIG.
11 is a graph showing the results of measurement of the transmittance of the super water-repellent PTFE thin film deposited according to the second embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

( First Embodiment )

FIG. 1 is a view showing the structure of a substrate on which a super-water-repellent PTFE thin film is deposited on a substrate according to a first embodiment of the present invention. FIG. 2 is a cross- Fig. 2 is a process flow chart for explaining a manufacturing method for the present invention.

The super-water-repellent PTFE thin film deposited on the substrate according to the present invention includes a substrate 10, a buffer layer 20 formed on the upper surface of the substrate 10, and a PTFE thin film 30 deposited on the upper surface of the buffer layer 20 .

In this case, the substrate 10 may be a metal substrate such as tin, aluminum or an alloy thereof, or may be a substrate made of various materials such as glass, sapphire, and silicon, if necessary. In this embodiment, ) Is made of aluminum will be described as an example.

In order to form a super-water-repellent PTFE thin film deposited on a substrate having the above-described structure, a super-water-repellent PTFE thin film is formed on the substrate 10 by a RF magnetron sputtering method, A thin film 30 is deposited. To this end, a PTFE target for thin film deposition is first fabricated (S10).

When the PTFE target is manufactured as described above, a cleaning step is performed to prepare the substrate 10 on which the PTFE thin film is to be deposited and to remove foreign matter adhering to the prepared substrate 10 (S20) The surface of the PTFE thin film 30 on which the PTFE thin film 30 is to be deposited is subjected to a surface treatment (S30) according to a suitable material.

After the step S30 is completed, the buffer layer 20 is formed on the upper surface of the substrate 10 (that is, the surface treated in the step S30) A step of depositing a thin film (S50) is performed.

Hereinafter, for convenience of explanation, a method of depositing the PTFE thin film 30 on the substrate 10 will be described separately.

① Step 1: PTFE target  Production stage ( S10 )

3 is a view showing the shape of a PTFE target produced for forming the PTFE thin film 30 on the aluminum substrate 10 according to the present embodiment.

In the present invention, a PTFE target is first formed to form a super-water-repellent PTFE thin film 30 on an aluminum substrate 10.

For this purpose, the original plate of the present embodiment, the PTFE Powder (F7 type, Solvay) for 2 hours in a ball mill process and 300 ^o diameter of the plastic and the pressure of 11 N / m ² for two hours in air at C 2-inch thick 5 mm And solidified through a pressing process with a pellet.

The PTFE thin film 30 is deposited on the aluminum substrate 10 by using a high-frequency magnetron sputtering method using the thus-prepared PTFE target as described later.

Step 2: Substrate preparation and cleaning step ( S20 )

Next, a substrate for forming a super-water-repellent PTFE thin film according to the present invention is prepared. In this embodiment, an aluminum substrate (Al5051) is used as the substrate.

Thus, when the substrate is prepared was conducted for each washing 15 minutes in the order of acetone, methanol, distilled water, at a temperature of about 50 ℃ the water bath using an ultrasonic cleaner to remove foreign materials on the substrate surface, then using the N ₂ gas All of the substrate moisture and dust were removed through a blowing process.

Step 3: Substrate surface treatment step ( S30 )

As is generally known, the water repellency of a superhydrophobic thin film having a large contact angle is affected by the microstructure formed on the surface of the substrate on which the thin film is formed and the low surface energy of the thin film.

Accordingly, in this embodiment, surface treatment is performed to form a microstructure on the surface of the aluminum substrate 10 on which the PTFE thin film is formed. For this purpose, in this embodiment, the aluminum substrate 10 10) was wet-etched.

At this time, dilute hydrochloric acid used in the wet etching was diluted with hydrochloric acid and water at a ratio of 8: 2. After about 10 minutes had elapsed so that diluted hydrochloric acid was mixed well, the aluminum substrate 10 was etched for about 20 minutes.

In the etching process, since the Al ₂ O ₃ layer, which is an oxide film, covers the surface of the aluminum substrate, the reaction rate is slow while the oxide film is removed by etching, but after about 10 minutes after the oxide film is removed, A microstructure is formed on the surface of the substrate 10 by the reaction of the aluminum layer.

After the etching process was completed, the substrate was washed with acetone, methanol and distilled water at a temperature of about 50 ° C for 15 minutes using an ultrasonic cleaner in order to remove impurities, etc., The completed substrate 10 has removed moisture and dust from the substrate through a blowing process using nitrogen (N 2) gas.

In this embodiment, the substrate having been blown is heated at a temperature of about 70 DEG C at normal pressure using an oven to remove any remaining moisture, and then stored in a vacuum state.

④ Stage 4: Buffer layer  Formation step ( S40 )

The buffer layer 20 is formed on the surface of the substrate 10 after the step S30 is completed to increase the water repellency of the PTFE thin film before the PTFE thin film is deposited.

In general, the PTFE thin film is known to have water repellency because of its very low surface energy. However, when it is deposited on a substrate, the adhesive force with the substrate is lowered due to low surface energy. Therefore, There is a disadvantage that the water repellency is gradually lowered due to the development.

Therefore, in order to solve the above disadvantages, the buffer layer 20 is formed on the surface of the substrate 10 using the SiO ₂ material in order to further increase the water repellency of the PTFE thin film.

At this time, the buffer layer 20 is formed by a high frequency magnetron sputtering method using an SiO ₂ target in the same manner as the PTFE thin film described later. In this embodiment, the buffer layer 20 is formed to a thickness of about several nm.

⑤ Step 5: PTFE  Thin film deposition step ( S50 )

When the buffer layer 20 is formed on the surface of the substrate 10 as described above, the PTFE thin film is deposited on the buffer layer 20 by a high-frequency magnetron sputtering method.

The high-frequency magnetron sputtering method is a sputtering method using both an electric field and a magnetic field. It can use both an insulator and a conductor target and can deposit a thin film of a higher quality than a chemical vapor deposition (CVD) method or other physical vapor deposition There is an advantage to be able to do.

In the high-frequency magnetron sputtering method, an AC voltage having a period smaller than 1/2 of the time required for charging the insulating target should be applied so that no charge accumulation occurs on the surface of the target. For this purpose, in this embodiment, An AC voltage having a frequency of 13.56 HHz was applied.

In the high-frequency magnetron sputtering method, a planar permanent magnet is disposed at a lower portion of a target opposite to the upper substrate so that electrons around the target are restrained by a magnetic field so as to rotate in a helical orbit without departing from the periphery of the target. Deposition can be performed even at a low gas pressure, and deterioration of physical properties of the substrate caused by electrons deviating from the target collides with the substrate can be prevented.

In this embodiment, the PTFE thin film is deposited on the aluminum substrate 10 on which the buffer layer 20 is formed by the high-frequency magnetron sputtering method, and the specific conditions of the deposition process used herein are shown in Table 1 below .

Process Variables of High Frequency Magnetron Sputtering Distance between substrate and target (mm) 60 Applied power (W) 50 Ar gas partial pressure (sccm) 20 Operating pressure (torr) 7.2 to 7.5 X 10 ^-2 Deposition time 30 (sec),
1,2,3,4,5,10,15,20,30 (min) Board Surface treated with wet etch
Aluminum (Al5051) substrate

Various experiments were carried out to investigate the water repellency and optical properties of the PTFE thin films deposited as described above.

4 is a graph showing changes in the contact angle depending on the deposition time of the thin film in the case of performing the surface treatment and the case of not performing the surface treatment in order to examine the effect of the surface treatment step of the substrate 10 performed in this embodiment on the water repellency And FIG. 5 is a view for explaining a method of measuring the contact angle used at this time.

Generally, when measuring the contact angle of a thin film, a micropump is used to lower a needle onto a substrate with a few drops of water droplets attached to a needle, then attaching water droplets to the substrate, raising the needle back to its original position , This moment is photographed with a CCD camera and the image is analyzed and the contact angle is measured by the method shown in FIG.

As shown in FIG. 4, when the etching process is not performed, there is a slight difference in the contact angle depending on the deposition time. However, the contact angle is about 125 ° To 130 [deg.].

On the other hand, when the etching process is performed, there is a slight difference according to the increase of the deposition time, but the contact angle is about 150 °. When the microstructure is formed on the surface of the substrate 10 by the etching process, the water repellency .

However, when the etching process is performed, the contact angle reaches a maximum value of about 155 ° in the initial 30 seconds (the thickness of the thin film is about 30 nm), and the deposition time is about 10 minutes (the thickness of the thin film is about 600 nm) The contact angle of the substrate surface was maintained at about 150 ° and thereafter the contact angle was gradually decreased. As the deposition time increased, the thicker film was etched to cover the microstructure formed on the surface of the aluminum substrate 10, It is believed that the micropores disappear.

In order to confirm this experimentally, the SEM surface image of the surface-treated substrate was examined according to the increase of the deposition time, and the result is shown in FIG.

6 shows the SEM surface image of the substrate after 30 seconds, 1 minute, 15 minutes, and 30 minutes of deposition time, respectively. When a PTFE thin film was deposited on the substrate surface-treated by etching, The micropores and structures were formed on the surface of the thin film due to the microstructure formed on the substrate. As the deposition time increased, the micropores and structures gradually decreased.

Due to the change of the SEM surface image, the contact angle of the PTFE thin film was increased due to the micropore structure and the structure formed on the surface of the PTFE film at the initial stage of deposition. However, as the deposition time increased, It can be seen that the contact angle gradually decreases due to disappearance.

Therefore, it is most preferable that the thickness of the PTFE thin film deposited on the surface-treated substrate is determined to be 30 nm to 600 nm.

7 and 8 are graphs showing the results of the surface treatment step of the substrate 10 and the case of not depositing the PTFE thin film and the deposition of the PTFE thin film in order to confirm the water- ≪ tb > < TABLE >

The X-ray photoelectron spectroscopy (XPS) analysis can analyze the kinetic energy of the electrons emitted when the internal orbital electrons are emitted by X-rays to analyze the binding energy and elements inside the atoms.

In general, the intensity of the individual atoms which increase the wettability of the organic surface is as follows.

F <H <Cl <Br <I <O <N

The order of decreasing the wettability among the fluorocarbon and hydrocarbon groups on the polymer surface having the lowest wettability is as follows

CF ₃ - <-CF ₂ - <CH ₃ - <-CH ₂ -

The PTFE thin film, which is a super-water-repellent thin film applied in the present invention, is composed of molecular bonds of C and F like CF ₃ , CF ₂ , CF-CF _n , C-CF _n and CC. Their bonding energies are 293.3 eV ₃ ), 291.3 eV (CF ₂ ), 289.3 eV (CF-CF _n ), 286.5 eV (C-CF _n ) and 284.5 eV (CC).

Therefore, it can be seen that the surface energy of the PTFE thin film is lowered when the surface is bonded with CF ₃ or CF ₂ radicals.

As shown in FIG. 7, in the XPS analysis of the substrate 10 without the PTFE thin film deposited, neither CF ₃ nor CF ₂ bonds lowering the surface energy are shown. Only CC and C═O bonds appear, Respectively.

On the other hand, as shown in FIG. 8, the XPS analysis of the substrate 10 in the state where the PTFE thin film was deposited showed that the CF ₃ bond was also formed mainly in the CF ₂ bond, and the surface energy was relatively low.

Therefore, it can be seen that the super-water repellent PTFE thin film according to the present invention exhibits a high contact angle and super-water repellency due to such low surface energy.

9 is a graph showing the change in the contact angle depending on the deposition time of the thin film compared with the case where the buffer layer is formed and the case where the buffer layer is not formed in order to evaluate the effect of the buffer layer formed in the super water repellent PTFE thin film according to the present invention on the water repellency Fig.

9, the contact angle becomes larger when the SiO ₂ buffer layer 20 is formed. This is because the PTFE thin film, which is non-tacky and has low surface energy as described above, is peeled off from the substrate 10 It is believed that the buffer layer 20 made of SiO ₂ prevents the contact angle from being lowered.

The super water-repellent property of the super-water-repellent PTFE thin film according to the present invention formed as described above is shown in FIG.

( Second Embodiment )

The present embodiment differs from the first embodiment in that the substrate 10 is made of a glass material rather than a metal material, and the surface treatment process (step S30) of the substrate is different from that of the first embodiment Hereinafter, the same reference numerals are assigned to the same components and process steps, and redundant description will be omitted.

In this embodiment, since the substrate 10 is a glass substrate, a plasma etching process is performed instead of wet etching as a surface treatment step.

In this embodiment, surface treatment of the substrate is performed by high-frequency magnetron sputtering using O ₂ gas as the source gas. The specific etching conditions are shown in Table 2 below.

Plasma etching conditions for glass substrates Etching source O ₂ (20 sccm) power 25W, 50W, 75W, 100W, 125W Etching time 60 min Working pressure 1.0 X 10 ^-5 torr

In order to experimentally confirm the optical characteristics of the PTFE thin film deposited on the glass substrate in the above-described manner, the transmittance change was measured using a UV-VIS Spectro photometer (Shimadzu Co.).

The transmittance measuring apparatus can measure the optical constants (refractive index, light absorption coefficient, etc.) by Modified Envelope method by measuring light transmittance in a wavelength range of 200 nm to 800 nm. For the base line alignment, Place the reference cell and calculate the ratio of the amount of light incident on the integrating sphere through the spectrophotometer in the UV lamp as an electrical signal.

This is to accurately detect the change in the amount of light at a specific wavelength depending on the time of the UV-lamp which changes with time. When the base line is sorted by wavelength, the sample to be analyzed is placed in the sample 2, , And the light transmittance by wavelength is measured.

At this time, when the reference is placed in Sample 1, the transmittance is measured only for the thin film. If nothing is placed, the transmittance of the sample is measured.

FIG. 11 shows the result of measuring the transmittance after depositing the PTFE thin film for 30 seconds by the high frequency magnetron sputtering after performing the plasma etching process as described above.

As can be seen from the measurement results, it was confirmed that the light transmittance did not change greatly when the thin film was deposited in comparison with the glass substrate on which the PTFE thin film was not deposited.

In addition, since the PTFE thin film deposited on the glass substrate according to the present invention exhibits a transmittance of 90% or more, which is higher than the transmittance of 85% required by the display display element, the ultra-water repellent PTFE thin film according to the present invention It can be applied to

10: substrate 20: buffer layer
30: PTFE thin film

Claims (6)

A substrate having an upper surface surface-processed to form a microstructure;
A buffer layer of SiO ₂ material deposited on the upper surface of the substrate;
And a PTFE thin film layer deposited on an upper surface of the buffer layer,
Wherein the buffer layer and the PTFE thin film layer are each deposited by a high frequency magnetron sputtering method. The method according to claim 1,
Wherein the substrate is an aluminum substrate,
Wherein the surface treatment is performed by wet etching using diluted hydrochloric acid. The method according to claim 1,
Wherein the substrate is a glass substrate,
Wherein the surface treatment is performed by plasma etching using O ₂ gas. A super-water-repellent PTFE thin film deposited on a substrate. A first step of surface-treating a substrate made of a metallic material or glass to form a microstructure on an upper surface thereof;
A second step of depositing a buffer layer of SiO ₂ material on the upper surface of the substrate; And
And a third step of depositing a PTFE thin film layer on the upper surface of the buffer layer,
Wherein the buffer layer and the PTFE thin film layer are deposited by a high frequency magnetron sputtering method in the second and third steps, respectively. 5. The method of claim 4,
Wherein the substrate is an aluminum substrate,
Wherein the surface treatment is performed by wet etching using diluted hydrochloric acid in the first step. 5. The method of claim 4,
Wherein the substrate is a glass substrate,
Wherein the surface treatment in the first step is performed by plasma etching using O ₂ gas.

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