KR100624627B1 - Method of superhydrophilic modification of polyvinylidene fluoride surface - Google Patents

Abstract

The present invention provides a method of modifying the surface of a PVDF to a superhydrophilic surface by irradiating a polyvinylidene fluoride surface with an activation beam having an ultra low energy of 10-90 eV and a high energy density of 0.5 mW / cm ² or more. In the present invention, the contact angle for distilled water is reduced at 61 ^o with little surface damage for a short time. Lowered to less than 2 ^o provides a method of modifying the PVDF surface to a superhydrophilic surface with a surface energy of at least 80 mN / m. The PVDF surface modified by the present invention has increased adhesion to metals, conductive polymers, transparent electrode materials, etc., so that the hydrophilization of the ultrafiltration membrane, the hydrogen ion conductive polyvinylidene fluorine resin membrane, and the transparent flexible speaker and the display and speaker integrated Flexible audio-video / audible display speakers, etc.

Ultra low energy activated beam, polyimide, polyvinylidene fluoride, piezoelectric material, contact angle, surface energy, adhesion, audio display, transparent flexible speaker

Description

Superhydrophilic Modification Method of Polyvinylidene Fluoride Surface {METHOD OF SUPERHYDROPHILIC MODIFICATION OF POLYVINYLIDENE FLUORIDE SURFACE}

1 is a graph illustrating an energy distribution of an Ar activation beam extracted after forming an Ar gas plasma using a discharge voltage of 230 V using a retarding field energy analyzer.

FIG. 2 shows the energy distribution of an activation beam measured by installing an attenuation electric field +100 V in front of a closed electron-hole drift activation beam source to reduce the energy of the activation beam under the condition of FIG. graph.

FIG. 3 is a graph showing the change in contact angle between a PVDF surface that is not surface treated and a PVDF surface treated with an Ar, N ₂ O, O ₂ activation beam. FIG.

4 shows an untreated PVDF surface (a), a PVDF surface treated with an argon activation beam (b), a PVDF surface treated with a nitrogen dioxide activation beam (c), and a PVDF surface treated with an oxygen activated beam (left, contact angle: Photo showing contact angles above 2 ^o ) and untreated PVDF surface (right) (d).

FIG. 5 shows the chemical composition of the PVDF surface untreated in FIG. 3 and the PVDF surface treated with Ar, N ₂ O, O ₂ activation beams irradiated in a wide energy region, where binding energy is measured in the region of 0-1400 eV. Graph showing -ray photoelectron spectroscopy results.

FIG. 6 is a detailed measurement of electron binding energy levels of (a) C1s, (b) O1s, (c) N1s, and (d) F1s. Electron core level X-ray photoelectron spectroscopy energy spectrum showing changes in amount of O, F.

7 is a photograph showing the roughness change of the PVDF surface and the surface treated by various activation beams untreated in FIG.

8 is a schematic representation of an apparatus for generating high density plasma in a closed electron-hole drift.

The present invention relates to a method for modifying the surface of a PVDF to a superhydrophilic surface by irradiating a polyvinylidene fluoride surface with an activation beam having an ultra low energy of 10-90 eV and a high energy density of 0.5 mW / cm ² or more.

Polyvinylidene fluoride, a piezoelectric polymer, is widely used as a material for infrared sensors, micro actuators, ultrasonic transducers, nonvolatile memory devices, and membranes due to chemical / thermal stability and electrical insulation.

When used as an ultrafiltration membrane made of PVDF, hydrophobic properties may cause problems such as separation of biomaterials due to deposition of proteins due to hydrophobic properties, and low adhesion to metals, ceramics and other polymer materials due to low surface energy. Increasing surface energy through surface treatment is essential.

In the case of polyvinylidene fluoride, the contact angle to distilled water is mostly about 61-90 ^o , and the initial surface energy is very low, about 44 mN / m. Thus, the surface treatment can be applied to metals, ceramics or other functional chemical groups. Many pretreatment methods have been studied.

Methods of improving these hydrophobic properties include chemical methods and etching [F. F. Stengnard et al., J. Membrane Sci. 36, 257 (1988); A. Khodai-Joopary et al., Nucl. Tracks Radiat. Meas. 15, 167 (1988)], radiochemical grafting [H. Iwata et al., J. Membrane Sci. 38, 38 (1988)] and the dip coating method [S. Kristensen, L. Cecille, J.C. Toussaint (Eds.), Future Industrial Prospects of Membrane Process, Elsevier, London, 118 (1989)] or physically using electrons, gamma rays, X-rays, and recently using plasma and ion beams.

According to YW Park et al., Polymer, 44, 1569 (2003), when using chemically activated plasmas and ion beams, argon, hydrogen, and oxygen gas are increased in the RF region to 25-100 W. When the PVDF surface was treated after activating the remote plasma while the contact angle was changed before and after argon, hydrogen, and oxygen treatment, the contact angle of the distilled water was investigated.The contact angle was measured from 90 ^o before 55 ^o , 53 ^o , and 71 ^o. Could only be reduced to a degree.

On the other hand, MD Duca et al., Polymer Degradation and Stability, 61, 65 (1998) reported that the contact angle for initial distilled water was 71 ^o when Ar gas was directly treated with a PVDF surface about 5 cm away using RF plasma. It is disclosed that it can be reduced to up to 36 ^o , thereby increasing the surface energy from 33 mN / m to 60 mN / m.

In addition, in recent literature, Han et al., J. Appl. Poymer Sci. 72, 41 (1997)], when the argon ion beam of about 1 keV is irradiated on the surface of PVDF, the initial contact angle of 75 ^o is reduced only to about 50 ^o , but when the reactive gas is blown to the surface of PVDF, the contact angle is up to 30 ^o . An ion assisted reaction (IAR) has been reported that can lower the Pt thin film on the surface of the PVDF treated as described above. However, no surface modification method has been reported so far with a contact angle of less than 30 ^° and little damage to the surface.

It is an object of the present invention to directly irradiate an ultra-low energy and high energy density activation beam with little damage to the polyvinylidene fluoride surface for a short irradiation time and to greatly increase the surface energy of the polyvinylidene fluoride at room temperature to increase other metals, It is to provide a method that can greatly improve the adhesion with ceramic, heterogeneous polymer.

The inventors of the present invention have a very low energy of about 10-90 eV and directly irradiate the surface with an activating beam having a high energy density of 0.5 W / cm ² or more so that the polyvinylidene fluoride surface is hardly damaged for a short irradiation time within 1 second. The present invention was completed by discovering that the surface energy of polyvinylidene fluoride can be increased to 80 mN / m or more at room temperature.

Accordingly, the present invention provides a method of modifying the surface of a PVDF to a superhydrophilic surface by irradiating a polyvinylidene fluoride surface with an activation beam having an ultra low energy of 10-90 eV and a high energy density of 0.5 mW / cm ² or more. .

More specifically, the method of modifying the surface of the PVDF of the present invention to a superhydrophilic surface to generate a gas plasma having a high energy density of 0.5 mW / cm ² or more, irradiating an electron beam to the ion beam in the generated gas plasma to neutral Generating an activation beam, applying a deceleration energy electric field between the polyvinylidene fluoride (PVDF) and the activation beam source to adjust the activation beam to ultra low energy of 10-90 eV and the ultra low energy activation beam to the PVDF surface Irradiating the PVDF surface.

In one embodiment of the present invention, the gas used to generate the gas plasma is oxygen or nitrous oxide or mixtures thereof, and within one second of irradiation can reduce the contact angle of the surface of the PVDF substrate to less than 2 ^o .

In another embodiment of the present invention the gas used to generate the gas plasma is a mixture of an inert gas and a reactive gas, where the inert gas is Ar, Kr, Xe or Ne, and the reactive gas is O ₂ , O ₃ , N ₂ O, NO ₂ or CO ₂ .

In the present invention, a low energy activation beam is irradiated onto a PVDF surface having a low surface energy to minimize surface damage due to ion collision, and at the same time, an ultra low energy capable of irradiating a chemically reactive activated beam to make a hydrophilic bond on the surface. Use an activation beam.

Ionizing neutral atoms or molecules causes electrons to be lost in most cases, turning into positively charged ions. Applying a voltage to these positive charges yields kinetic energy equal to the applied voltage, and these particles are transformed into states that have the ability to work. It is said that the energy-enhanced state is activated, and when an ion beam having such energy is caused to be neutralized when it is incident on a sample together with electrons, it has energy but acts as an electrically neutral particle, and thus "ion beam Instead of "," it is expressed as "activation beam."

In order to make an ultra low energy (10-90 eV), high density activated beam in the present invention, a high density plasma of about 10 ¹² / cm ³ was first generated by a closed electron-hole drift. The energy distribution of the activation beam extracted from the plasma has about 2 / 3-3 / 4 of the discharge voltage V _d .

An embodiment using argon will be described with reference to FIG. 8, when argon gas is flowed into the cathode 4 and discharged at several hundred volts, electrons are generated. Some of the electrons generated at this time are accelerated in the direction of the anode 3. When it accelerates, it rotates by the magnetic field 1 of the magnet installed outside the channel 2, colliding with the gas incident near the anode, forming a plasma, and eventually hitting the anode, and disappearing. At this time, the positively charged particles in the ionized gas are accelerated from the anode toward the sample. At this time, the energy of the positive charge has an energy corresponding to about 2/3 to 3/4 of the discharge voltage V _d between the anode and the cathode. For example, when V _d is 230 eV, the acceleration energy of the argon cation measured by the energy analyzer was measured to be 178 eV.

When such a positive charge hits the surface of an insulator sample such as a polymer or an oxide, electrons near the surface of the sample are extracted in a vacuum, and the initial electrical state, which was neutral, exhibits positive electricity due to the decrease in the number of electrons. The cation further increases the positive electricity, causing the sample to turn into a positively charged material. This phenomenon is called charge-up. However, in the case of the closed electron-hole ion beam, in addition to accelerating electrons generated at the cathode to the anode, some of them participate in the flow of the cationic particles and serve to supply the amount of the negative charge to the sample surface. That is, the positive charge changes to neutral particles having neutralized energy, which is incident on the surface of the sample, resulting in a neutralization effect of removing the positive charge accumulation phenomenon.

1 is an energy distribution measurement result for the Ar activation beam as described above. At the discharge voltage V _d = 230 eV, the average energy of the argon activated beam was about 178 eV, and the degree of energy dispersion was about σ _E = ± 20.5 eV.

Meanwhile, the energy distribution of the activation beam measured by adjusting the energy of the activation beam measured by creating a retarding energy field between the PVDF and the activation beam source was measured.

The cations ionized by the electrons accelerated from the cathode to the accelerated anode retain and hold 2 / 3-3 / 4 of the discharge voltage V _d between the cathode and the anode. For example, when V _d = 230 eV, the acceleration energy of the argon cation measured by the energy analyzer was measured to be 178 eV. At this time, install a tungsten wire (diameter 4 mm) 20 mm larger than the size of the ion beam extracted from the ion source at a distance of 100 mm from the ion source, and apply a retarding voltage of V _r = + 100V. When applied, the energy of the positively charged ion beam can be reduced by V _r . Figure 2 is a graph showing the energy distribution of the cation thus obtained, the average energy is about 80 eV, the degree of energy spread slightly increased to σ _E = ± 25 eV. In this way, each activation beam can be adjusted to very low energy of about 10-90 eV.

3 shows deionized distilled water for a PVDF surface irradiated with PVDF surface for 1 second at an average energy of 80 eV after generating a low energy activation beam using an untreated PVDF surface and Ar, N ₂ O, O ₂ gas. It is a graph showing the change of contact angle measured.

As described above, Ar, N ₂ O, O ₂ gas is allowed to flow between the channels of the ion source, and in the case of Ar, the plasma is formed by electrons at a discharge voltage of 230 eV, and in the case of N ₂ O and O ₂ , respectively, 300 eV. The energy of Ar ⁺ , N ₂ O ^_ , O ₂ ⁺ ion beams attenuated to 80 eV on average was irradiated onto the surface of PVDF.

As shown in the figure, a PVDF surface not treated with an activating beam shows a contact angle of about 61 degrees, but a contact angle of about 35 ^o when treated with an Ar activation beam and 4 ^o and 2 ^o when treated with nitrogen dioxide and oxygen, respectively. Is showing. This suggests that treatment with an activation beam containing oxygen, which is a reactive gas, is very effective in lowering the contact angle, and in the case of oxygen, PVDF can be treated with superhydrophilic surfaces with a contact angle of less than 2 ^o to deionized distilled water. Can be.

FIG. 4 is a photograph of contact angles measured by a computer automation program using a contact angle measuring device for contact angles between distilled water and PVDF surfaces under each condition measured in FIG. 3. (a) is the untreated PVDF surface (contact angle: 61 ^o ), (b) is the PVDF surface treated with argon activation beam (contact angle: 30 ^o ), (c) is the PVDF surface treated with nitrogen dioxide activated beam (contact angle : 4 ^o ), (d) Photograph showing the contact angle on the PVDF surface (left side, contact angle: less than 2 ^o ) and the untreated PVDF surface (right side) treated with an oxygen activation beam.

FIG. 5 is a graph showing X-ray photoelectron spectroscopy results of irradiating a chemical composition of a PVDF surface treated with Ar, N ₂ O, and O ₂ activating beams in a large energy region, where binding energy was measured in the 0-1400 eV region.

In the case of PVDF not treated with an activating beam, only C1s and F1s peaks due to [-CH ₂ -CF _2- ] coupling are observed. In PVDFs treated with Ar-activated beams, the C1s peak intensity is greatly increased, due to the large defluoridation of light F elements into the vacuum due to the transfer of momentum by large masses when the Ar-activated beams strike the PVDF surface. It is shown that the amount of carbon atoms is relatively increased to increase the C1s peak. Carbons missing elemental fluorine have a slight O1s peak observed by bonding with residual oxygen gas or water in the vacuum chamber. When treated with nitrous oxide (N ₂ O), less defluorination occurs than in the case of Ar activation beam, and F1s are present at a relatively higher ratio than C1s, and oxygen and nitrogen components that bind carbon are observed. . When irradiated with an oxygen-activated beam having a smaller mass than nitrous oxide, defluorination occurs less than nitrous oxide, but it can be seen that the amount of oxygen bound to carbon increases significantly.

6 is a detailed measurement of the electron binding energy level of (a) C1s, (b) O1s, (c) N1s and (d) F1s in each case to more accurately understand the above results, Electron core level X-ray photoelectron spectroscopic energy spectrum showing changes in the C, N, O and F amounts of PVDF.

Tables 1 and 3 compare the amounts of elements present on each PVDF surface in percentage.

PVDF surface C N O F Untreated surface 51.19 0 1.03 47.79 Ar activated beam 79.5 0.28 7.31 12.91 N ₂ O activated beam 67.13 5.99 10.11 16.78 O ₂ activated beam 64.5 3.76 14.74 17.0

As shown in Table 1, the ratio of C: N: O: F for the untreated PVDF shows 51.2%: 0%: 1.03%: 47.79%. For PVDF surface-treated using Ar, N ₂ O, and O ₂ activation beams, the amount of carbon increases most at 79.5% for Ar and slightly lowers at 67.13% and 64.5% for N ₂ O and O ₂ , respectively. It is higher than the case without treatment. On the other hand, fluorine decreases by 12.91% in Ar and almost similarly decreases in N ₂ O and O ₂ by 16.78 and 17.0%, respectively. This indicates that the CH and CF bonds of [-CH ₂ -CF _2- ], the main components of PVDF, are broken by the activation beam, and the volatile H and F are evaporating into the vacuum. You can see only the remains. However, when looking at the amount of nitrogen change, it can be seen that N ₂ O contains 5.99% of oxygen and 14.74% of oxygen when irradiated with oxygen. It can be seen that it is well formed and forms hydrophilic functional groups such as CN and C═O. In particular, the irradiation with the oxygen beam is in good agreement with the result showing the lowest contact angle when the highest oxygen content is included.

FIG. 6 shows changes in surface roughness with atomic force microscope images of the surface of PVDF treated before and before surface treatment with various activation beams.

The surface roughness of the untreated PVDF is about 5.5 nm, slightly flattened by about 4.5 nm when using an argon activation beam, and further decreased by 4.25 nm when irradiated with nitrous oxide activation beam.

In the case of using the oxygen activation beam, it increases slightly to about 6 nm, but in all cases, it shows only a change within ± 1 nm with respect to the surface roughness of the untreated PVDF, using an ultra low energy, high energy density activation beam according to the present invention. It can be seen that the treatment of the PVDF surface does not cause any damage to the surface.

According to the method of the present invention, since the surface of most hydrophobic polymers containing fluorine (-F-) can be made hydrophilic without damage, the polymer can be used as a substrate for high value electronic components, and piezoelectric using PVDF It can be applied to the development of new materials, component materials with excellent stability and durability through improved adhesion to metals during device fabrication.

In addition, after forming a transparent conductive polymer and an oxide thin film on PVDF, a flexible audible display can be fabricated using a metal electrode and used as a surface treatment technology of a separator material capable of remarkably improving the movement of photons in a battery using hydrogen. Can be used.

Claims (4)

Generating a gas plasma having a high energy density in the range of 0.5 to 1.5 mW / cm ² , Irradiating an electron beam to the ion beam in the generated gas plasma to generate a neutral activation beam, Applying a deceleration energy electric field between polyvinylidene fluoride (PVDF) and the activation beam source to adjust the activation beam to ultra low energy of 10-90 eV; and Irradiating the ultra-low energy activated beam onto a PVDF surface A method of modifying the surface of the PVDF to a superhydrophilic surface comprising a. The method of claim 1, wherein the gas is oxygen or nitrous oxide or mixtures thereof and lowers the contact angle of the surface of the PVDF substrate material to less than 2 ^o within 1 second after irradiation. The method of claim 1, wherein the gas is a mixture of an inert gas and a reactive gas, wherein the inert gas is Ar, Kr, Xe or Ne, and the reactive gas is O ₂ , O ₃ , N ₂ O, NO ₂ or CO ₂ . Way. The method of claim 1, wherein the surface energy of the PVDF increases in the range of 80 to 90 mN / m.

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