Patent Application
20080118770
The present invention relates to a method for manufacturing an ultra-hydrophilic thin film coated metal product, and an ultra-hydrophilic thin film coated metal product.
Metal materials having hydrophilic surface layers on their surfaces have been efficiently used in the whole industrial fields, which will now be explained by using a heat exchanger as an example.
A heat exchanger exchanging heat by making two fluids having different temperatures directly or indirectly contact each other has been widely used in various industrial fields, especially for heating, air conditioning, power generation, waste heat recovery and chemical processes.
An air conditioning heat exchanger forms a fin that is an enlarged surface at the air side to improve heat transmission. When the air having humidity passes through the fin in the heat exchange operation, heat transmission occurs by low temperature refrigerants supplied into a tube. When a temperature of the surface of the fin is equal to or lower than a dew point temperature of the air having humidity, droplets are formed on the surface of the heat exchanger to intercept flow of the air, which increases a pressure drop that is a pressure difference between the inlet and outlet of the heat exchanger. Accordingly, power of a fan must be increased to supply the same flux, which results in large power consumption.
In order to solve the above problem, as disclosed in Japanese Laid-Open Patent Application 61-8598, flow of condensed water formed on a surface of a fin of a heat exchanger is improved by performing an anti-corrosive process on an aluminum sheet of the fin by using Cr+6 to improve corrosion resistance, and performing a silicate-group coating process thereon to give hydrophilicity, which is called a pre-coated material (PCM).
The PCM basically requires Cr+6 to obtain corrosion resistance. However, Cr+6 will be prevented since 2006 due to environmental problems. There are thus increasing demands for a material substituting for Cr+6. Until now, Cr+3 or resin type has been suggested. In the preparation of the PCM, tetrachloroethane (TCE) inevitably used to wash aluminum also causes environmental contamination. In addition, the PCM showing excellent hydrophilic performance at an initial stage gradually loses the hydrophilic property, namely, has an aging characteristic. Recently, chemical products have been mostly used as materials for wallpaper. The silicate material for giving hydrophilicity is volatilized and chemically coupled with the wall paper, thereby discoloring the wall paper. Also, the volatilized materials displease people.
Continuous attempts have been made to satisfy various demands by forming a functional surface layer (for example, hydrophilicity or hydrophobicity) on the existing material. Exemplary methods for forming the functional surface layer include 1) depositing the functional surface layer on the existing material, and 2) giving new physical and chemical properties by improving the surface film of the existing material.
However, in the latter, as the time elapses, the surface property is changed and returns to the original property. For example, in the case that a metal such as aluminum is processed according to an ion beam assisted reaction process, hydrophilicity of the surface of the metal is improved. It is because a natural oxide film is etched on the surface of the aluminum and the functional film is formed thereon. As the time elapses, an oxide film is naturally grown on the surface of the aluminum. As a result, hydrophilicity improvement effects obtained by etching the natural oxide film are deteriorated. The functional film formed on the surface of the aluminum is made of an extremely thin layer (<a few nm) having very low mechanical resistance to environmental variations (water, temperature, etc.) by time. Accordingly, the improved hydrophilic property is reduced and returns to the original surface property.
In order to solve the foregoing problem, efforts have been continuously made to form on a metal material a hydrophilic or hydrophobic functional surface layer that can maintain a physically chemically stable state.
For example, as suggested in Japanese Laid-Open Patent Application 2001-280879, in a heat exchanger mounting a fin made of a conductive metal material on a metal tube that is a refrigerant passage, compound vapor containing titanium that is raw gas is supplied to flow in parallel to the surface of the fin of the heat exchanger in the air. Therefore, the heat exchanger coating the titanium dioxide thin film on the surface of the fin is manufactured according to a plasma CVD technology. The above patent application teaches that the heat exchanger can obtain excellent hydrophilic, antibacterial and deodorizing properties.
However, in a state where the fin is mounted on the tube to compose the heat exchanger, the titanium dioxide thin film is deposited on the fin of the heat exchanger. Thus, the titanium dioxide thin film cannot be uniformly deposited on the whole surface of the fin, which deteriorates hydrophilic and aging properties. Furthermore, productivity for direct application to the industrial production is not attained.
The present invention is achieved to solve the above problems. An object of the present invention is to provide a method for manufacturing an ultra-hydrophilic thin film coated metal product having excellent hydrophilic and aging properties, and an ultra-hydrophilic thin film coated metal product.
Another object of the present invention is to easily produce an ultra-hydrophilic thin film on an industrial production scale, by forming the ultra-hydrophilic thin film on a sheet-shaped metal substrate and mechanically processing the metal substrate into a target shape.
Yet another object of the present invention is to uniformly form an ultra-hydrophilic thin film on both surfaces of a sheet-shaped metal substrate.
In order to achieve the above-described objects of the invention, there is provided a method for manufacturing a ultra-hydrophilic thin film coated metal product, which continuously coats a ultra-hydrophilic titanium compound thin film on both surfaces of a continuously-supplied sheet-shaped metal substrate in a vacuum chamber by using plasma, and mechanically processes the thin film coated sheet into a target shape. Here, the thin film is a Ti—O group compound thin film. Preferably, the thin film is a Ti—O group compound thin film containing 15 to 22 atomic % of Ti and 45 to 65 atomic % of O. In addition, the thin film further contains C and/or H. Preferably, the thin film contains 15 to 22 atomic % of Ti and 45 to 65 atomic % of O, and further contains 20 to 25 atomic % of C and/or 20 to 25 atomic % of H. Here, the thin film has a thickness of 1 to 100 nm.
The metal substrate can be an aluminum substrate, and the metal product can be a fin for a heat exchanger.
The coating process is performed by injecting reactive gas, gas-phase titanium precursor and carrier gas into the vacuum chamber. Preferably, the gas injection ratio satisfies carrier gas:reactive gas=1:3, and also satisfies gas-phase titanium precursor:carrier gas=3:1.
Preferably, the reactive gas is air or O2, the carrier gas is selected from the group consisting of He, N2 and Ar, and the gas-phase titanium precursor is prepared by passing liquid-phase titanium tetraisopropoxide through a bubbler. In addition, the injection amount of the gas-phase titanium precursor into the vacuum chamber is controlled by adjusting the amount of the liquid-phase titanium tetraisopropoxide supplied to the bubbler. The carrier gas is injected before the liquid-phase titanium tetraisopropoxide is injected into the bubbler, for transferring the liquid-phase titanium tetraisopropoxide to the bubbler.
There is also provided a ultra-hydrophilic thin film coated metal product, which is coated with a ultra-hydrophilic Ti—O group compound thin film containing 15 to 22 atomic % of Ti and 45 to 65 atomic % of O at a thickness of 1 to 100 nm by using plasma. Preferably, the thin film further contains 20 to 25 atomic % of C and/or 20 to 25 atomic % of H. The thin film has an amorphous structure and the metal sheet is an aluminum sheet. The thin film coated aluminum sheet is a metal sheet that can be mechanically processed into a fin for a heat exchanger.
The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein:
a and 5b are photographs respectively showing dispersion of droplets when the surface is hydrophilic (
A method for manufacturing a ultra-hydrophilic thin film coated metal product, and a ultra-hydrophilic thin film coated metal product in accordance with the present invention will now be described in detail with reference to the accompanying drawings.
A vacuum pump 4 for forming a vacuum inside the coating chamber 2 is connected to the coating chamber 2, and a metal sheet 8 is continuously supplied between electrodes 6 installed at the upper and right portions or the right and left sides. In
Preferably, a reactive gas cylinder 20 containing reactive gas that can form air or oxygen injects the reactive gas to the coating chamber 2 through a valve 22.
In addition, a liquid-phase titanium precursor that is liquid-phase titanium tetraisopropoxide [Ti(OC3H7)4] contained in a containing vessel 30 pressurized by a pressurizer 32 is injected into a bubbler 40 through a liquid-phase mass flow controller (MFC) 38 due to pressure differences. A gas-phase titanium precursor bubbled by the bubbler 40 is injected into the coating member 2. Preferably, carrier gas that can form He, Ar or N2 is injected through a tube between the liquid-phase MFC 38 and the bubbler 40, for helping the gas-phase titanium precursor to be injected into the coating chamber 2. The carrier gas is contained in a carrier gas cylinder 50 and injected into the tube through a valve 52. A heater coil 42 is coiled around the bubbler 40 to heat and bubble the liquid-phase titanium precursor. As described above, the coating process using nano plasma is executed by injecting the reactive gas that can form air or O2, the gas-phase titanium precursor and the carrier gas into the coating chamber 2. The injection amount of the gas-phase titanium precursor into the coating chamber 2 is controlled by adjusting the amount of the liquid-phase precursor supplied to the bubbler 40, namely, the liquid-phase titanium tetraisopropoxide.
Here, the reactive gas, the gas-phase titanium precursor and the carrier gas can be combined outside the coating chamber 2 and injected into the coating chamber 2 through one tube 60 as shown in
The gas-phase titanium precursor is condensed at a low temperature. When the tube 60 is maintained at a normal temperature, the gas-phase titanium precursor is condensed on the inner wall of the tube 60. In order to prevent condensation of the gas-phase titanium precursor, a hot wire 64 is coiled around the outer wall of the tube 60 through which the gas-phase titanium precursor gas flows, for maintaining a predetermined temperature. A tube 66 through which the liquid-phase titanium precursor flows is also formed in the same manner. That is, a hot wire 68 is coiled around the outer wall of the tube 66, for maintaining a predetermined temperature, thereby preventing the titanium precursor from being condensed on the inner wall of the tube 66.
In accordance with the present invention, the ultra-hydrophilic titanium compound thin film is continuously coated on the metal sheet 8 continuously supplied to the coating chamber 2 by using the plasma, and the thin film coated metal sheet 8 is mechanically processed into a target shape, for example, a fin of an air conditioning heat exchanger.
As illustrated in
Preferably, the reactive gas cylinder 20 containing the reactive gas that can form air or oxygen injects the reactive gas to the coating chamber 2 through the valve 22.
In addition, the liquid-phase titanium precursor that is liquid-phase titanium tetraisopropoxide [Ti(OC3H7)4] contained in the containing vessel 30 pressurized by the pressurizer 32 is injected into the bubbler 40 through the liquid-phase MFC 38 due to pressure differences. The gas-phase titanium precursor bubbled by the bubbler 40 is injected into the coating member 2. Preferably, the carrier gas that can form He or Ar is injected through the tube between the liquid-phase MFC 38 and the bubbler 40, for helping the gas-phase titanium precursor and the gas-phase silicon precursor to be injected into the coating chamber 2. The carrier gas is contained in the carrier gas cylinder 50 and injected into the tube through the valve 52. The heater coil 42 is coiled around the bubbler 40 to heat and bubble the liquid-phase titanium precursor.
Here, the reactive gas, the gas-phase titanium or silicon precursor and the carrier gas can be combined outside the coating chamber 2 and injected into the coating chamber 2 through one tube 60 as shown in
The gas-phase titanium or silicon precursor is condensed at a low temperature. When the tube 60 is maintained at a normal temperature, the gas-phase titanium precursor is condensed on the inner wall of the tube 60. In order to prevent condensation of the gas-phase titanium precursor, the hot wire 64 is coiled around the outer wall of the tube 60 through which the gas-phase titanium precursor gas flows, for maintaining a predetermined temperature. The tube 66 through which the liquid-phase titanium precursor flows is also formed in the same manner. That is, the hot wire 68 is coiled around the outer wall of the tube 66, for maintaining a predetermined temperature, thereby preventing the titanium or silicon precursor from being condensed on the inner wall of the tube 66.
Reference numerals 34 and 36 denote a valve of the pressurizer 32 and a valve of the containing vessel 30, respectively.
In accordance with the present invention, the ultra-hydrophilic Ti—O—C group compound thin film is continuously coated on the metal sheet 8 continuously supplied to the coating chamber 2 by using the plasma, and the thin film coated metal sheet 8 is mechanically processed into a target shape, for example, a fin of an air conditioning heat exchanger.
The ultra-hydrophilic metal sheet can be manufactured by using the plasma polymerization device. As mentioned above, the ultra-hydrophilic metal sheet is mechanically processed into the fin of the heat exchanger, and physical and surface properties thereof are measured and explained in the following examples. It must be recognized that the scope of the present invention is not restricted by the following examples but claims recited below.
Preparation of Plasma Coating Film
After 10−3 Torr of vacuum was formed in the coating chamber 2 by using the vacuum pump 4, the metal sheet 8 was connected to an anode and maintained at a predetermined distance (30 to 150 mm) from the electrodes 6, and the heater coil 42 of the bubbler 40 was electrically heated (80 to 120° C.) to bubble the liquid-phase precursor. The hot wires 64 and 68 coiled around the outer walls of the tubes 60 and 66 were electrically heated (80 to 120° C.) to prevent the titanium precursor from being condensed on the inner walls of the tubes 60 and 66. The gas-phase precursor gas, the carrier gas and the reactive gas were injected into the coating chamber 2 through the tube, and discharged in the up/down direction of the metal sheet 8.
Preferably, the gas-phase precursor gas and the carrier gas were injected into the coating chamber 2 at a ratio of 3:1, and the carrier gas and the reactive gas were injected into the coating chamber 2 at a ratio of 1:3.
When a target operation vacuum degree was obtained by the injected gas, the power was turned on, the metal sheet 8 was transferred in regard to the tube 60, and the plasma was continuously formed between the electrodes 6 by the mixed gas. Accordingly, the ultra-hydrophilic Ti—O—C group compound thin film was coated on both surfaces of the metal sheet 6.
In the plasma treatment, the current was 1.2 A 900V, the flux of the carrier gas that is He or Ar gas was 800 sccm, the flux of the reactive gas that was oxygen or air was 1500 sccm, the flux of the gas-phase precursor gas was 1000 sccm, and the vacuum degree inside the chamber 2 ranged from 0.2 to 0.35 Torr.
Analysis of Composition and Thickness of Coated Thin Film
The composition of the processed thin film sample was analyzed according to X-ray photoelectric spectroscopy (XPS) for analogizing surface composition by measuring molecular specific absorption and emission wavelengths by using X-rays, and the thickness thereof was analyzed according to atomic emission spectrometry (AES) for analyzing composition by depth by performing sputtering at a fixed speed.
Although not illustrated, when only the ultra-hydrophilic compound thin film was coated, the Ti—O—C group compound thin film was prepared.
In accordance with the analysis results, although slightly varied upon the conditions, the titanium compound thin film commonly contains 15 to 22 atomic % of Ti, 45 to 65 atomic % of O, and 20 to 25 atomic % of C and/or 20 to 25 atomic % of H.
Hydrophilic and Aging Properties of Thin Film
The hydrophilic performance test was executed by dropping a fixed quantity of droplets (0.1 cc) from a height of 10 mm, and measuring a size of droplets on the surface of the sample. When the surface of the film was hydrophilic, the size of the droplets increased due to high dispersion, and when the surface of the film was hydrophobic, the size of the droplets decreased due to low dispersion.
In order to evaluate the hydrophilic aging property, the samples were cyclically put into distilled water for 10 minutes and dried for 10 minutes. The hydrophilic performance of the initial samples was compared with that of the samples obtained after 300 cycles.
Hydrophilic Performance Property by Manufactured Composition
The heating temperature of the bubbler 40 for bubbling the liquid-phase precursor was set as 60° C., 100° C. and 120° C. The liquid-phase precursor heated and bubbled at 100° C. had the highest hydrophilic performance (8.7 mm).
The reactive gas was changed into O2, N2 and air. The sample using the air as the reactive gas had the highest hydrophilic performance (9.3 mm).
The carrier gas was changed into He and Ar. The sample using He as the carrier gas had the highest hydrophilic performance (9.9 mm).
The deposition time of the precursor gas was changed between 30 sec and 120 sec at an interval of 30 sec. The sample passing through 90 sec coating showed similar hydrophilic performance to that of the sample passing through 120 sec coating (9.9 mm). Accordingly, the coating process was preferably performed for 90 sec, to maintain the hydrophilic performance and reduce the production time.
Here, the current of the electrodes 6 installed on both surfaces of the sample for forming the plasma was 0.13 A, and the vacuum inside the coating chamber 2 housing the sample was maintained at 0.3 Torr.
In order to efficiently manufacture the ultra-hydrophilic thin film coated metal product, the liquid-phase precursor was heated and bubbled at 100° C. in the bubbler 40, the air was used as the reactive gas, He was used as the carrier gas, and the coating process was executed in the chamber 2 for 90 sec.
In the above test, the coating process was executed on the suitable sample. In the mass-production of the products, the heating temperature of the bubbler, the reactive gas, the carrier gas and the deposition time can be varied within the approximate range according to production environments and variable factors by continuous mass-production.
As discussed earlier, in accordance with the present invention, the air conditioning metal material coated with the thin film having excellent hydrophilic and aging properties can be easily produced on an industrial production scale.
In addition, the ultra-hydrophilic thin film can be uniformly formed on both surfaces of the sheet-shaped metal substrate.
Although the preferred embodiments of the present invention have been described, it is understood that the present invention should not be limited to these preferred embodiments but various changes and modifications can be made by one skilled in the art within the spirit and scope of the present invention as hereinafter claimed.
The present invention relates to a method for manufacturing an ultra-hydrophilic thin film coated metal product, and an ultra-hydrophilic thin film coated metal product.
Metal materials having hydrophilic surface layers on their surfaces have been efficiently used in the whole industrial fields, which will now be explained by using a heat exchanger as an example.
A heat exchanger exchanging heat by making two fluids having different temperatures directly or indirectly contact each other has been widely used in various industrial fields, especially for heating, air conditioning, power generation, waste heat recovery and chemical processes.
An air conditioning heat exchanger forms a fin that is an enlarged surface at the air side to improve heat transmission. When the air having humidity passes through the fin in the heat exchange operation, heat transmission occurs by low temperature refrigerants supplied into a tube. When a temperature of the surface of the fin is equal to or lower than a dew point temperature of the air having humidity, droplets are formed on the surface of the heat exchanger to intercept flow of the air, which increases a pressure drop that is a pressure difference between the inlet and outlet of the heat exchanger. Accordingly, power of a fan must be increased to supply the same flux, which results in large power consumption.
In order to solve the above problem, as disclosed in Japanese Laid-Open Patent Application 61-8598, flow of condensed water formed on a surface of a fin of a heat exchanger is improved by performing an anti-corrosive process on an aluminum sheet of the fin by using Cr+6 to improve corrosion resistance, and performing a silicate-group coating process thereon to give hydrophilicity, which is called a pre-coated material (PCM).
The PCM basically requires Cr+6 to obtain corrosion resistance. However, Cr+6 will be prevented since 2006 due to environmental problems. There are thus increasing demands for a material substituting for Cr+6. Until now, Cr+3 or resin type has been suggested. In the preparation of the PCM, tetrachloroethane (TCE) inevitably used to wash aluminum also causes environmental contamination. In addition, the PCM showing excellent hydrophilic performance at an initial stage gradually loses the hydrophilic property, namely, has an aging characteristic. Recently, chemical products have been mostly used as materials for wallpaper. The silicate material for giving hydrophilicity is volatilized and chemically coupled with the wall paper, thereby discoloring the wall paper. Also, the volatilized materials displease people.
Continuous attempts have been made to satisfy various demands by forming a functional surface layer (for example, hydrophilicity or hydrophobicity) on the existing material. Exemplary methods for forming the functional surface layer include 1) depositing the functional surface layer on the existing material, and 2) giving new physical and chemical properties by improving the surface film of the existing material.
However, in the latter, as the time elapses, the surface property is changed and returns to the original property. For example, in the case that a metal such as aluminum is processed according to an ion beam assisted reaction process, hydrophilicity of the surface of the metal is improved. It is because a natural oxide film is etched on the surface of the aluminum and the functional film is formed thereon. As the time elapses, an oxide film is naturally grown on the surface of the aluminum. As a result, hydrophilicity improvement effects obtained by etching the natural oxide film are deteriorated. The functional film formed on the surface of the aluminum is made of an extremely thin layer (<a few nm) having very low mechanical resistance to environmental variations (water, temperature, etc.) by time. Accordingly, the improved hydrophilic property is reduced and returns to the original surface property.
In order to solve the foregoing problem, efforts have been continuously made to form on a metal material a hydrophilic or hydrophobic functional surface layer that can maintain a physically chemically stable state.
For example, as suggested in Japanese Laid-Open Patent Application 2001-280879, in a heat exchanger mounting a fin made of a conductive metal material on a metal tube that is a refrigerant passage, compound vapor containing titanium that is raw gas is supplied to flow in parallel to the surface of the fin of the heat exchanger in the air. Therefore, the heat exchanger coating the titanium dioxide thin film on the surface of the fin is manufactured according to a plasma CVD technology. The above patent application teaches that the heat exchanger can obtain excellent hydrophilic, antibacterial and deodorizing properties.
However, in a state where the fin is mounted on the tube to compose the heat exchanger, the titanium dioxide thin film is deposited on the fin of the heat exchanger. Thus, the titanium dioxide thin film cannot be uniformly deposited on the whole surface of the fin, which deteriorates hydrophilic and aging properties. Furthermore, productivity for direct application to the industrial production is not attained.
The present invention is achieved to solve the above problems. An object of the present invention is to provide a method for manufacturing an ultra-hydrophilic thin film coated metal product having excellent hydrophilic and aging properties, and an ultra-hydrophilic thin film coated metal product.
Another object of the present invention is to easily produce an ultra-hydrophilic thin film on an industrial production scale, by forming the ultra-hydrophilic thin film on a sheet-shaped metal substrate and mechanically processing the metal substrate into a target shape.
Yet another object of the present invention is to uniformly form an ultra-hydrophilic thin film on both surfaces of a sheet-shaped metal substrate.
In order to achieve the above-described objects of the invention, there is provided a method for manufacturing a ultra-hydrophilic thin film coated metal product, which continuously coats a ultra-hydrophilic titanium compound thin film on both surfaces of a continuously-supplied sheet-shaped metal substrate in a vacuum chamber by using plasma, and mechanically processes the thin film coated sheet into a target shape. Here, the thin film is a Ti—O group compound thin film. Preferably, the thin film is a Ti—O group compound thin film containing 15 to 22 atomic % of Ti and 45 to 65 atomic % of O. In addition, the thin film further contains C and/or H. Preferably, the thin film contains 15 to 22 atomic % of Ti and 45 to 65 atomic % of O, and further contains 20 to 25 atomic % of C and/or 20 to 25 atomic % of H. Here, the thin film has a thickness of 1 to 100 nm.
The metal substrate can be an aluminum substrate, and the metal product can be a fin for a heat exchanger.
The coating process is performed by injecting reactive gas, gas-phase titanium precursor and carrier gas into the vacuum chamber. Preferably, the gas injection ratio satisfies carrier gas:reactive gas=1:3, and also satisfies gas-phase titanium precursor:carrier gas=3:1.
Preferably, the reactive gas is air or O2, the carrier gas is selected from the group consisting of He, N2 and Ar, and the gas-phase titanium precursor is prepared by passing liquid-phase titanium tetraisopropoxide through a bubbler. In addition, the injection amount of the gas-phase titanium precursor into the vacuum chamber is controlled by adjusting the amount of the liquid-phase titanium tetraisopropoxide supplied to the bubbler. The carrier gas is injected before the liquid-phase titanium tetraisopropoxide is injected into the bubbler, for transferring the liquid-phase titanium tetraisopropoxide to the bubbler.
There is also provided a ultra-hydrophilic thin film coated metal product, which is coated with a ultra-hydrophilic Ti—O group compound thin film containing 15 to 22 atomic % of Ti and 45 to 65 atomic % of O at a thickness of 1 to 100 nm by using plasma. Preferably, the thin film further contains 20 to 25 atomic % of C and/or 20 to 25 atomic % of H. The thin film has an amorphous structure and the metal sheet is an aluminum sheet. The thin film coated aluminum sheet is a metal sheet that can be mechanically processed into a fin for a heat exchanger.
The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein:
a and 5b are photographs respectively showing dispersion of droplets when the surface is hydrophilic (
A method for manufacturing a ultra-hydrophilic thin film coated metal product, and a ultra-hydrophilic thin film coated metal product in accordance with the present invention will now be described in detail with reference to the accompanying drawings.
A vacuum pump 4 for forming a vacuum inside the coating chamber 2 is connected to the coating chamber 2, and a metal sheet 8 is continuously supplied between electrodes 6 installed at the upper and right portions or the right and left sides. In
Preferably, a reactive gas cylinder 20 containing reactive gas that can form air or oxygen injects the reactive gas to the coating chamber 2 through a valve 22.
In addition, a liquid-phase titanium precursor that is liquid-phase titanium tetraisopropoxide [Ti(OC3H7)4] contained in a containing vessel 30 pressurized by a pressurizer 32 is injected into a bubbler 40 through a liquid-phase mass flow controller (MFC) 38 due to pressure differences. A gas-phase titanium precursor bubbled by the bubbler 40 is injected into the coating member 2. Preferably, carrier gas that can form He, Ar or N2 is injected through a tube between the liquid-phase MFC 38 and the bubbler 40, for helping the gas-phase titanium precursor to be injected into the coating chamber 2. The carrier gas is contained in a carrier gas cylinder 50 and injected into the tube through a valve 52. A heater coil 42 is coiled around the bubbler 40 to heat and bubble the liquid-phase titanium precursor. As described above, the coating process using nano plasma is executed by injecting the reactive gas that can form air or O2, the gas-phase titanium precursor and the carrier gas into the coating chamber 2. The injection amount of the gas-phase titanium precursor into the coating chamber 2 is controlled by adjusting the amount of the liquid-phase precursor supplied to the bubbler 40, namely, the liquid-phase titanium tetraisopropoxide.
Here, the reactive gas, the gas-phase titanium precursor and the carrier gas can be combined outside the coating chamber 2 and injected into the coating chamber 2 through one tube 60 as shown in
The gas-phase titanium precursor is condensed at a low temperature. When the tube 60 is maintained at a normal temperature, the gas-phase titanium precursor is condensed on the inner wall of the tube 60. In order to prevent condensation of the gas-phase titanium precursor, a hot wire 64 is coiled around the outer wall of the tube 60 through which the gas-phase titanium precursor gas flows, for maintaining a predetermined temperature. A tube 66 through which the liquid-phase titanium precursor flows is also formed in the same manner. That is, a hot wire 68 is coiled around the outer wall of the tube 66, for maintaining a predetermined temperature, thereby preventing the titanium precursor from being condensed on the inner wall of the tube 66.
In accordance with the present invention, the ultra-hydrophilic titanium compound thin film is continuously coated on the metal sheet 8 continuously supplied to the coating chamber 2 by using the plasma, and the thin film coated metal sheet 8 is mechanically processed into a target shape, for example, a fin of an air conditioning heat exchanger.
As illustrated in
Preferably, the reactive gas cylinder 20 containing the reactive gas that can form air or oxygen injects the reactive gas to the coating chamber 2 through the valve 22.
In addition, the liquid-phase titanium precursor that is liquid-phase titanium tetraisopropoxide [Ti(OC3H7)4] contained in the containing vessel 30 pressurized by the pressurizer 32 is injected into the bubbler 40 through the liquid-phase MFC 38 due to pressure differences. The gas-phase titanium precursor bubbled by the bubbler 40 is injected into the coating member 2. Preferably, the carrier gas that can form He or Ar is injected through the tube between the liquid-phase MFC 38 and the bubbler 40, for helping the gas-phase titanium precursor and the gas-phase silicon precursor to be injected into the coating chamber 2. The carrier gas is contained in the carrier gas cylinder 50 and injected into the tube through the valve 52. The heater coil 42 is coiled around the bubbler 40 to heat and bubble the liquid-phase titanium precursor.
Here, the reactive gas, the gas-phase titanium or silicon precursor and the carrier gas can be combined outside the coating chamber 2 and injected into the coating chamber 2 through one tube 60 as shown in
The gas-phase titanium or silicon precursor is condensed at a low temperature. When the tube 60 is maintained at a normal temperature, the gas-phase titanium precursor is condensed on the inner wall of the tube 60. In order to prevent condensation of the gas-phase titanium precursor, the hot wire 64 is coiled around the outer wall of the tube 60 through which the gas-phase titanium precursor gas flows, for maintaining a predetermined temperature. The tube 66 through which the liquid-phase titanium precursor flows is also formed in the same manner. That is, the hot wire 68 is coiled around the outer wall of the tube 66, for maintaining a predetermined temperature, thereby preventing the titanium or silicon precursor from being condensed on the inner wall of the tube 66.
Reference numerals 34 and 36 denote a valve of the pressurizer 32 and a valve of the containing vessel 30, respectively.
In accordance with the present invention, the ultra-hydrophilic Ti—O—C group compound thin film is continuously coated on the metal sheet 8 continuously supplied to the coating chamber 2 by using the plasma, and the thin film coated metal sheet 8 is mechanically processed into a target shape, for example, a fin of an air conditioning heat exchanger.
The ultra-hydrophilic metal sheet can be manufactured by using the plasma polymerization device. As mentioned above, the ultra-hydrophilic metal sheet is mechanically processed into the fin of the heat exchanger, and physical and surface properties thereof are measured and explained in the following examples. It must be recognized that the scope of the present invention is not restricted by the following examples but claims recited below.
Preparation of Plasma Coating Film
After 10−3 Torr of vacuum was formed in the coating chamber 2 by using the vacuum pump 4, the metal sheet 8 was connected to an anode and maintained at a predetermined distance (30 to 150 mm) from the electrodes 6, and the heater coil 42 of the bubbler 40 was electrically heated (80 to 120° C.) to bubble the liquid-phase precursor. The hot wires 64 and 68 coiled around the outer walls of the tubes 60 and 66 were electrically heated (80 to 120° C.) to prevent the titanium precursor from being condensed on the inner walls of the tubes 60 and 66. The gas-phase precursor gas, the carrier gas and the reactive gas were injected into the coating chamber 2 through the tube, and discharged in the up/down direction of the metal sheet 8.
Preferably, the gas-phase precursor gas and the carrier gas were injected into the coating chamber 2 at a ratio of 3:1, and the carrier gas and the reactive gas were injected into the coating chamber 2 at a ratio of 1:3.
When a target operation vacuum degree was obtained by the injected gas, the power was turned on, the metal sheet 8 was transferred in regard to the tube 60, and the plasma was continuously formed between the electrodes 6 by the mixed gas. Accordingly, the ultra-hydrophilic Ti—O—C group compound thin film was coated on both surfaces of the metal sheet 6.
In the plasma treatment, the current was 1.2 A 900V, the flux of the carrier gas that is He or Ar gas was 800 sccm, the flux of the reactive gas that was oxygen or air was 1500 sccm, the flux of the gas-phase precursor gas was 1000 sccm, and the vacuum degree inside the chamber 2 ranged from 0.2 to 0.35 Torr.
Analysis of Composition and Thickness of Coated Thin Film
The composition of the processed thin film sample was analyzed according to X-ray photoelectric spectroscopy (XPS) for analogizing surface composition by measuring molecular specific absorption and emission wavelengths by using X-rays, and the thickness thereof was analyzed according to atomic emission spectrometry (AES) for analyzing composition by depth by performing sputtering at a fixed speed.
Although not illustrated, when only the ultra-hydrophilic compound thin film was coated, the Ti—O—C group compound thin film was prepared.
In accordance with the analysis results, although slightly varied upon the conditions, the titanium compound thin film commonly contains 15 to 22 atomic % of Ti, 45 to 65 atomic % of O, and 20 to 25 atomic % of C and/or 20 to 25 atomic % of H.
Hydrophilic and Aging Properties of Thin Film
The hydrophilic performance test was executed by dropping a fixed quantity of droplets (0.1 cc) from a height of 10 mm, and measuring a size of droplets on the surface of the sample. When the surface of the film was hydrophilic, the size of the droplets increased due to high dispersion, and when the surface of the film was hydrophobic, the size of the droplets decreased due to low dispersion.
In order to evaluate the hydrophilic aging property, the samples were cyclically put into distilled water for 10 minutes and dried for 10 minutes. The hydrophilic performance of the initial samples was compared with that of the samples obtained after 300 cycles.
Hydrophilic Performance Property by Manufactured Composition
The heating temperature of the bubbler 40 for bubbling the liquid-phase precursor was set as 60° C., 100° C. and 120° C. The liquid-phase precursor heated and bubbled at 100° C. had the highest hydrophilic performance (8.7 mm).
The reactive gas was changed into O2, N2 and air. The sample using the air as the reactive gas had the highest hydrophilic performance (9.3 mm).
The carrier gas was changed into He and Ar. The sample using He as the carrier gas had the highest hydrophilic performance (9.9 mm).
The deposition time of the precursor gas was changed between 30 sec and 120 sec at an interval of 30 sec. The sample passing through 90 sec coating showed similar hydrophilic performance to that of the sample passing through 120 sec coating (9.9 mm). Accordingly, the coating process was preferably performed for 90 sec, to maintain the hydrophilic performance and reduce the production time.
Here, the current of the electrodes 6 installed on both surfaces of the sample for forming the plasma was 0.13 A, and the vacuum inside the coating chamber 2 housing the sample was maintained at 0.3 Torr.
In order to efficiently manufacture the ultra-hydrophilic thin film coated metal product, the liquid-phase precursor was heated and bubbled at 100° C. in the bubbler 40, the air was used as the reactive gas, He was used as the carrier gas, and the coating process was executed in the chamber 2 for 90 sec.
In the above test, the coating process was executed on the suitable sample. In the mass-production of the products, the heating temperature of the bubbler, the reactive gas, the carrier gas and the deposition time can be varied within the approximate range according to production environments and variable factors by continuous mass-production.
As discussed earlier, in accordance with the present invention, the air conditioning metal material coated with the thin film having excellent hydrophilic and aging properties can be easily produced on an industrial production scale.
In addition, the ultra-hydrophilic thin film can be uniformly formed on both surfaces of the sheet-shaped metal substrate.
Although the preferred embodiments of the present invention have been described, it is understood that the present invention should not be limited to these preferred embodiments but various changes and modifications can be made by one skilled in the art within the spirit and scope of the present invention as hereinafter claimed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2004-0023446 | Apr 2004 | KR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR04/02868 | 11/6/2004 | WO | 00 | 10/24/2007 |
