Polymer thin film with water repellency and oil repellency and method for preparing the same

Abstract

This disclosure relates to a method for preparing a polymer thin film with water repellency and oil repellency, including: thermally decomposing a thermal initiator to form a radical; reacting the radical with a monomer mixture of a specific composition to synthesize a polymer; and depositing the synthesized polymer on a substrate, and a polymer thin film with water repellency and oil repellency including a polymer resin including (meth)acrylate-based repeat units substituted with a fluorine-containing functional group and repeat units derived from a compound including at least two reactive functional groups at a specific ratio.

Claims

1. A polymer thin film comprising: a polymer resin comprising (meth)acrylate-based repeat units substituted with a fluorine-containing functional group; and repeat units derived from a reactive compound comprising at least two vinyl groups or (meth)acrylate-based functional groups at a mole ratio of 100:13 to 100:50, and having a static contact angle of 120° or more with 3 μl of distilled water and a static contact angle of 80° or more with 3 μl of oleic acid, wherein the polymer thin film has a sliding angle of 30° or less with 30 μl of oleic acid, and the polymer thin film has pencil hardness of HB or higher, as measured using a 500 g weight according to ASTM D3363.

2. The polymer thin film according to claim 1, wherein the polymer thin film has average surface roughness of 15 nm or less, and average surface roughness per 100 nm of 3 nm or less.

3. The polymer thin film according to claim 1, wherein the polymer thin film has a static contact angle of 120° to 140° with 3 μl of distilled water, and a static contact angle of 80° to 120° with 3 μl of oleic acid.

4. The polymer thin film according to claim 1, wherein the polymer thin film has a thickness of 10 nm to 1000 nm.

5. The polymer thin film according to claim 1, wherein the polymer resin has weight average molecular weight of 10,000 to 1,000,000.

6. The polymer thin film according to claim 1, wherein the polymer thin film is prepared by chemical vapor deposition using a thermal initiator.

7. The polymer thin film according to claim 6, wherein the chemical vapor deposition comprising the steps of: thermally decomposing the thermal initiator of a gas phase to form a radical; reacting the formed radical with a monomer mixture comprising (meth)acrylate-based monomers substituted with a fluorine-containing functional group and a reactive compound comprising at least two vinyl groups or (meth)acrylate-based functional groups to synthesize a polymer; and depositing the synthesized polymer on a substrate, wherein a ratio of deposition partial pressure of the following General Formula 1 of the reactive compound comprising at least two vinyl groups or (meth)acrylate-based functional groups to deposition partial pressure of the following General Formula 1 of the (meth)acrylate-based monomers substituted with a fluorine-containing functional group is 0.13 to 0.50:
Deposition partial pressure=Pm/Psat  [General Formula 1] wherein, in the General Formula 1, Psat denotes saturation vapor pressure of corresponding monomers or compounds at a surface temperature of a substrate on which the synthesized polymer is deposited, and Pm denotes partial pressure of corresponding monomers or compounds in a reactor in which the deposition is progressed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an atomic force microscope (AFM) image of the surface of the polymer thin film obtained in Example 1.

(2) FIG. 2 shows an atomic force microscope (AFM) image of the surface of the polymer thin film obtained in Example 2.

(3) FIG. 3 shows an atomic force microscope (AFM) image of the surface of the polymer thin film obtained in Example 3.

(4) FIG. 4 shows an atomic force microscope (AFM) image of the surface of the polymer thin film obtained in Comparative Example 1.

(5) FIG. 5 shows an atomic force microscope (AFM) image of the surface of the polymer thin film obtained in Comparative Example 2.

(6) FIG. 6 shows an atomic force microscope (AFM) image of the surface of the polymer thin film obtained in Comparative Example 3.

(7) FIG. 7 is a graph showing average surface roughness distribution per 100 nm thickness of the deposition film according to an EGDA/PFDA ratio.

(8) FIG. 8 is a graph showing distribution of an oleic acid sliding angle according to an EGDA/PFDA ratio.

(9) FIG. 9 shows comparison results of heat resistances of Example 1 and Comparative Example 2.

(10) FIG. 10 shows measurement results of chemical resistances of the surfaces of the polymer thin films obtained in Example 1 and Comparative Example 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(11) Hereinafter, specific embodiments of the invention will be explained in detail with reference to the following examples. However, these examples are only to illustrate specific embodiments of the invention, and the scope of the invention is not limited thereto.

Example: Preparation of Polymer Thin Film

(12) A deposition substrate of a silicon wafer was pretreated with oxygen plasma and positioned inside a hot wire chemical vapor deposition reactor. In the vapor deposition reactor, the temperature of the substrate surface was maintained at 20° C., a process pressure of 0.1 Torr was applied, and a nickel-chromium (8:2) hot wire was heated to 300° C.

(13) Further, 1H,1H,2H,2H-perfluorodecyl acrylate and ethylene glycol diacrylate of a gas phase were respectively introduced into the vapor deposition reactor while controlling the introduction amount using a metering valve. Herein, the applied temperature for vaporizing the 1H,1H,2H,2H-perfluorodecyl acrylate (PFDA) and ethylene glycol diacrylate (EGDA) and the degree of opening of the metering valve are as shown in the following Table 1.

(14) In the process of introducing the 1H,1H,2H,2H-perfluorodecyl acrylate and ethylene glycol diacrylate, vaporized tert-butyl peroxide was injected in an amount of 2 sccm using a mass flow controller.

(15) In Examples 1 and 2, deposition was progressed for about 15 minutes, and in Example 3, deposition was progressed for 5 minutes, to prepare polymer thin films.

Comparative Example 1: Preparation of Polymer Thin Film

(16) A polymer thin film was prepared by the same method as Example 1, except that the ethylene glycol diacrylate was not used, and the vaporization temperature and degree of opening of the metering valve as described in the following Table 1 were applied. Herein, in Comparative Example 1, deposition was progressed for about 30 minutes.

Comparative Examples 2 and 3: Preparation of Polymer Thin Films

(17) Polymer thin films of Comparative Example 2 and Comparative Example 3 were prepared by the same method as Example 1, except that ethylene glycol diacrylate was introduced in a relatively very small amount or in a relatively excessive amount as described in the following Table 1. Herein, in Comparative Examples 2 and 3, deposition was progressed for about 15 minutes.

EXPERIMENTAL EXAMPLE

Experimental Example 1: Analysis of Components of Deposition Film

(18) The components of the deposition films were analyzed using X-ray photoelectron spectroscopy (XPS or ESCA; model name: ESCALAB 250(VG)) under the following system conditions.

(19) TABLE-US-00001 TABLE 1 System conditions Conditions Base chamber pressure 3.0 × 10.sup.−10 mbar X-ray source Monochromatic Al Kα (1486.6 eV) X-ray spot size 400 μm Lens mode LargeAreaXL Operation mode CAE (Constant Analyzer Energy) mode Ar ion etching Etching rate~0.1 nm/sec (Mag 5, based on SiO.sub.2) Charge compensation Low energy electron flood gun, 3 eV

(20) Survey and narrow data were obtained with the parameters described in the following Table 2, and qualitative and quantitative coupling analysis was conducted.

(21) TABLE-US-00002 TABLE 2 Scan section Step Dwell Number of Pass Element binding energy size(eV) time scan energy Survey −5~1350 eV 1 50 ms 15 100 eV Narrow about ±15 eV, 0.1 50 ms 15~20  30 eV respectively * Peak background: Shirley background, average: 1 eV

(22) After a survey scan was conducted to qualitatively analyze whether or not C, O, and F atoms are contained, in order to confirm the mixing ratio of PFDA and EGDA, a narrow scan was conducted for a C 1s peak. Herein, in order to prevent confusion due to surface contamination, it was based on the contents detected within 10 nm in a depth direction from the surface.

(23) Peaks corresponding to binding energy known through C 1s peak deconvolution were confirmed. Carbon peaks relating to the deposition film are as follows: —C—C*H.sub.2—C— (285.0 eV), —C*H—CO— (285.7 eV), —O—C*H.sub.2—CH.sub.2— (286.7 eV), —CH.sub.2—C*H.sub.2—CF.sub.2— (286.8 eV), —O—C*═O— (289.2 eV), —C*F.sub.2— (291.2 eV), and —C*F.sub.3— (293.3 eV). Herein, in PFDA, 7 —C*F.sub.2—'s exist, and one —O—C*═O— exists per molecule. Further, since 2 O—C*═O—'s exist per molecule in EGDA, the area ratio of ‘—O—C*═O—’/‘-C*F.sub.2—’ in the peaks designated through C 1s peak deconvolution corresponds to ‘(PFDA mole number+EGDA mole number)/PFDA mole number’. From this, the mole ratios of 1H,1H,2H,2H-perfluorodecyl acrylate (PFDA) and ethylene glycol diacrylate (EGDA) in the polymer deposition film were respectively calculated and are shown in Table 3.

Experimental Example 2: Measurement of Surface Roughness

(24) A scan was conducted for a 5 μm×5 μm area in a tapping mode using an atomic force microscope (large stage AFM (Veeco Inc. Dimension 3100)) to measure average surface roughnesses of the polymer deposition thin films obtained in the examples and comparative examples.

(25) The atomic force microscope (AFM) images of the surfaces of the polymer thin films obtained in the examples and comparative examples are shown in FIGS. 1 to 6.

(26) As shown in FIGS. 1 to 3, it was confirmed that the surfaces of the polymer thin films obtained in Examples 1 to 3 show very flat shapes. However, in the case of Example 2, although surface roughness rather increases due to a thickness increase, average surface roughness per unit thickness is similar to Example 3, as shown in Table 3. To the contrary, in the case of Comparative Example 1 of FIG. 4, surface roughness appeared to be very large, and in the case of Comparative Example 2 of FIG. 5, surface roughness increased because of too low containing ratio of the reactive compound including at least two vinyl groups or (meth)acrylate-based functional groups.

(27) Average surface roughness distribution per 100 nm thickness according to EGDA/PFDA ratio is shown in FIG. 7. It can be seen that the ratio of EGDA/PFDA should be 0.10 or more so that the average surface roughness per 100 nm thickness of a deposition film may satisfy a level of 3 nm or less.

Experimental Example 3: Measurement of Static Contact Angle and Dynamic Contact Angle

(28) (1) Measurement of Static Contact Angle

(29) By a tangent method, 3 μl of each of water and oleic acid were put on the surfaces of the polymer deposition thin films obtained in the examples and comparative examples, and static contact angles were measured using a DSA 100 measuring device.

(30) As shown in Table 3, it was confirmed that in the case of Examples 1 to 3 containing a reactive compound (EGDA) including at least two vinyl groups or (meth)acrylate-based functional groups, the water contact angle and the oleic acid contact angle are not impeded, and water repellency and oil repellency equivalent to those of the polymer deposition film of Comparative Example 1 consisting only of (meth)acrylate-based monomers substituted with a fluorine-containing functional group are maintained.

(31) (2) Measurement of Dynamic Contact Angle

(32) After putting 30 μl of oleic acid on the surfaces of the polymer deposition thin films obtained in the examples and comparative examples, while raising one side of the stage to form an angle of inclination in the film, a sliding angle at which the oleic acid slides down was measured using a DSA 100 measuring device by a tilting table method.

(33) As shown in Table 3, in Comparative Example 3, the mole ratio of repeat units derived from a reactive compound (EGDA) including at least two vinyl groups or (meth)acrylate-based functional groups to the fluorine-containing functional group-substituted (meth)acrylate-based (PFDA) repeat units is too large, thus showing a high oleic acid sliding angle of 30° or more, which may be unfavorable for removal of surface contamination such as fingerprints. The distribution of the oleic acid sliding angle according to EGDA/PFDA ratio is shown in FIG. 8. The EGDA/PFDA ratio should be 0.8 or less so that oleic acid sliding angle may be 30° or less, when calculated according to the Equation (y=19.619x+14.147) obtained from the experiment results.

Experimental Example 4: Measurement of Mechanical Strength

(34) According to ASTM D3363, using a pencil hardness tester, pencil hardnesses of the surfaces of the polymer deposition thin films obtained in the examples and comparative examples were measured using a 500 g weight.

(35) As shown in Table 3, Comparative Example 1 wherein a reactive compound (EGDA) including at least two vinyl groups or (meth)acrylate-based functional groups is not included, and Comparative Example 2 wherein the containing ratio is too small, exhibited low mechanical strength of 3B or less, while Examples 1 to 3 wherein the containing ratio of the (meth)acrylate-based (PFDA) repeat substituted with a fluorine-containing functional group and the repeat units derived from a reactive compound (EGDA) including at least two vinyl groups or (meth)acrylate-based functional groups is 100:13 or more, exhibited pencil hardness of HB or higher.

Experimental Example 5: Measurement of Heat Resistance

(36) The polymer deposited specimens obtained in examples and comparative examples were heated in a 250° C. oven, and then the states of the thin film surfaces before and after heating were observed with a microscope.

(37) As shown in FIG. 9, on the surface of the polymer thin film of Example 1, there was no change before and after heating, while on the surface of the polymer thin film of Comparative Example 2, the surface shape was changed after heating. In the case of Comparative Example 2, although it is a crosslinked polymer film, since the mole ratio of the repeat units derived from a reactive compound (EGDA) including at least two vinyl groups or (meth)acrylate-based functional groups to the (meth)acrylate-based (PFDA) repeat units substituted with a fluorine-containing functional group is too small, the formed polymer thin film could not secure sufficient thermal stability.

Experimental Example 6: Measurement of Chemical Resistance

(38) 0.5 mL of hexafluoroisopropanol was added dropwise on the surfaces of the polymer deposition thin films of examples and comparative examples, and it was confirmed whether or not dissolution occurred.

(39) As shown in FIG. 10, the surface of the polymer thin film of Example 1 was not dissolved in hexafluoroisopropanol, while the surface of the polymer thin film of Comparative Example 1 was dissolved immediately when hexafluoroisopropanol was added dropwise.

(40) The results of the experimental examples are shown in Table 1.

(41) TABLE-US-00003 TABLE 3 Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 1 Example 2 Example 3 Vaporization PFDA 90 90 90 90 90 90 temperature EGDA 70 90 90 — 70 90 Scale of PFDA 7 7 7 9 7 7 metering valve [based on 10] EGDA 5 1 1 — 1 5 Deposition thickness 210 265 80 400 120 400 [nm] EGDA/PFDA ratio 0.34 0.165 0.15 0 0.095 0.9 Surface roughness 3.0 7.7 2.2 18.9 10.5 4.1 (Ra) [nm] Roughness per 100 nm 1.4 2.9 2.8 4.7 8.8 1.0 thickness [nm] Water contact angle 125.9 131.6 130.0 120.9 133.5 130.2 Oleic acid contact 94.2 97.1 91.4 89.7 99.2 96.1 angle Oleic acid sliding 20.6 17.2 16.9 13.9 16.5 31.9 angle Pencil hardness F HB HB <6B 3B 3H