Method for manufacturing large-pore anodized membrane by high-voltage anodization

Abstract

The present invention relates to: a method for anodizing phosphoric acid by application of a high voltage; and a method for preparing a large-pore anodized membrane by using same. More specifically, the present invention relates to: a method for anodization by application of a high voltage, which enables production of an anodized membrane having large pores of 200 nm or more by anodization in a phosphoric acid solution while sequentially increasing pressure and applying a high voltage of 190 V or more; a method for manufacturing a large-pore anodized membrane by using the method for anodization; and a large-area, large-pore anodized membrane manufactured thereby.

Description

Method for manufacturing a large-pore anodic oxidation membrane by high-voltage application anodic oxidation

[0001] The present invention relates to a method for phosphoric acid anodic oxidation by applying high voltage and a method for manufacturing a large-pore anodic oxidation membrane using the same. More specifically, the invention relates to an anodic oxidation method capable of manufacturing an anodic oxidation membrane having large pores of 200 nm or more by using a phosphoric acid solution as an electrolyte and stably applying a high voltage of 190 V to 200 V or more to anodic oxidation, and to a large-area, large-pore anodic oxidation membrane manufactured by the same.

[0002]

[0003] When aluminum is electrochemically anodic oxidized in an aqueous solution containing an electrolyte such as sulfuric acid, oxalic acid, or phosphoric acid, a thick anodic oxide film is formed on the surface.

[0004] Anodic oxide films exhibit minimal thermal deformation in high-temperature environments and possess electrical insulating properties. Research is underway to utilize these physical and / or electrical characteristics in various fields.

[0005] It is known that the structure of the porous layer and the boundary layer, such as the pore spacing, pore size, and boundary layer thickness, of such anodized films, which have regular spacing pores that grow from the outer surface toward the inner metal, is generally independent of the type or temperature of the electrolyte and is predominantly determined by the applied voltage.

[0006] It is known that well-aligned porous alumina oxide membranes are synthesized under specific anodic oxidation conditions depending on the electrolyte solution. Previously, there were many anodized aluminum membranes using sulfuric acid, phosphoric acid, or oxalic acid as electrolytes, but in each electrolyte, well-aligned anodic oxidation membranes were produced only under appropriate voltage conditions, and the controllable pore size was limited. In particular, it was known that in order to produce a large-pore anodic oxidation membrane of 100 nm or more, phosphoric acid must be used as the electrolyte and a voltage of 190 V or higher must be applied. However, when such high voltage of 190 V or higher is applied, a burning phenomenon occurs in which the aluminum metal burns during the anodizing process, so it is not known that large-pore anodic oxidation membranes can be produced over a large area.

[0007] Therefore, there were limitations in synthesizing anodic alumina films having large nanopores with a pore size of 150 nm or more using the conventional anodizing method with an electrolytic solution.

[0008] Accordingly, while conducting research in consideration of the technical limitations mentioned above, the inventors confirmed that even when anodizing with a voltage of 190V or higher is performed using a phosphoric acid solution as an electrolytic solution, a well-aligned anodic oxidized alumina membrane with large nanopores of 150 nm or more can be stably synthesized without surface burning by improving the voltage boosting process, and thus completed the present invention.

[0009]

[0010] The present invention aims to provide a high-voltage application anodic oxidation method that can stably manufacture a large-area anodic oxidation membrane of 10 cm x 10 cm or larger, which has a pore size of 150 nm or larger, by applying a high voltage to solve the problems of the conventional technology described above.

[0011] The present invention also aims to provide a large-area anodic oxidation membrane of 10 cm x 10 cm or larger, which is a large-area pore with a pore size of 150 nm or more, manufactured by the manufacturing method of the present invention.

[0012]

[0013] The present invention aims to solve the above-mentioned problems.

[0014] i) a step of preparing an aluminum substrate, for preparing an aluminum substrate;

[0015] ii) a first anodizing step of immersing the aluminum substrate in a solution containing phosphoric acid, maintaining the temperature of the solution containing phosphoric acid at -5°C to -2°C, and performing anodic oxidation while increasing the applied voltage from 10V to 195V to 200V to form a first anodic oxidation layer on the aluminum substrate;

[0016] iii) a first etching step for removing a first anodic oxide layer formed on the surface of the aluminum substrate; and

[0017] iv) a second anodizing step of immersing the aluminum substrate from which the first anodic oxide layer has been removed in a solution containing phosphoric acid, maintaining the temperature of the solution containing phosphoric acid at -5°C to -2°C, and performing anodic oxidation while increasing the applied voltage from 10V to 195V to 200V to form a second anodic oxide layer on the aluminum substrate; the present invention provides a method for manufacturing an anodic oxide membrane by high-voltage applied anodic oxidation, comprising: iv) a second anodizing step of immersing the aluminum substrate from which the first anodic oxide layer has been removed in a solution containing phosphoric acid, maintaining the temperature of the solution containing phosphoric acid at -5°C to -2°C, and performing anodic oxidation while increasing the applied voltage from 10V to 195V to 200V to form a second anodic oxide layer on the aluminum substrate.

[0018] The method for manufacturing an anodic oxidation membrane according to the present invention is characterized by making the voltage step-up profile up to 170 V and the voltage step-up profile above 170 V different in order to solve the problem of burning occurring on the aluminum surface when a high voltage of 170 V or higher is applied while the anodic oxidation process in a phosphoric acid solution is stable up to 170 V, thereby enabling the stable production of a seed for forming an anodic oxidation membrane.

[0019] In a method for manufacturing an anodic oxidation membrane by high-voltage application anodic oxidation according to the present invention,

[0020] The above-mentioned first anodizing step comprises a 1-1 step-up step of performing anodizing while increasing the applied voltage from 10V to 170V;

[0021] A first-second step-up stage for performing anodizing while increasing the applied voltage from 170V to 175V;

[0022] A first-third step-up step of performing anodizing while increasing the applied voltage from 175V to 195V to 200V; and

[0023] A first-to-fourth step-up step of performing anodizing while maintaining the applied voltage at 195V to 200V; comprising,

[0024] In the above 1-1 boosting step

[0025] Anodizing is performed by maintaining an applied voltage of 10V and a current limit of 0.5A for 60 seconds, and then the applied voltage is gradually increased at a rate of 10V / 1 time, and anodizing is performed by maintaining the increased voltage for 60 seconds, thereby sequentially increasing the applied voltage up to 170V.

[0026] In the above 1st-2nd boosting stage

[0027] After performing anodizing at a boosted voltage of 170V while maintaining a current limit of 0.5A for 30 seconds, the applied voltage is then boosted by 5V to 175V, and anodizing is performed while maintaining the boosted voltage for 3 hours.

[0028] In the above 1st-3rd boosting stages

[0029] Set the current limit to 0.5A, increase the applied voltage from 170V to 195V or 200V at a rate of 1V / 1 cycle, and perform anodizing while maintaining the increased voltage for 6 seconds.

[0030] In the above 1st-4th boosting steps

[0031] It is characterized by performing anodizing for 15 hours while maintaining a current limit of 0.5A at an applied voltage of 195V to 200V.

[0032] In the method for manufacturing an anodic oxidation membrane by high-voltage application anodic oxidation according to the present invention, the second anodizing step

[0033] 2-1 step-up, which performs anodizing while stepping up the applied voltage from 10V to 190V;

[0034] A 2-2 step-up step of performing anodizing while increasing the applied voltage from 190V to 195 to 200V; and

[0035] A second-third step-up step of performing anodizing while maintaining an applied voltage of 195 to 200V; comprising,

[0036] In the above 2-1 boosting step

[0037] Anodizing is performed by maintaining the voltage for 60 seconds at an applied voltage of 10V and a current limit of 0.5A, and then anodizing is performed by increasing the voltage at a rate of 10V / 1 time and maintaining the increased voltage for 60 seconds, thereby performing anodizing while sequentially increasing the applied voltage up to 190V.

[0038] In the above 2-2 boosting step

[0039] Perform anodizing while maintaining the voltage at an applied voltage of 190V and a current limit of 0.5A for 30 seconds, and thereafter, increase the applied voltage by 5V in one step with a current limit of 0.5A to 195V to 200V, and perform anodizing while maintaining the increased voltage for 30 seconds.

[0040] In the above 2nd-3rd boosting stage

[0041] It is characterized by performing anodizing while maintaining a final applied voltage of 195V to 200V and a current limit of 0.5A for 15 hours.

[0042] The method for manufacturing an anodic oxidation membrane according to the present invention is characterized by applying a high voltage of 195V to 200V in a phosphoric acid solution so that a seed for forming an anodic oxidation membrane including an aligned hexagonal structure can be stably manufactured.

[0043] In a method for manufacturing an anodic oxidation membrane by high voltage application anodic oxidation according to the present invention, the solution containing phosphoric acid is characterized by maintaining the concentration of phosphoric acid at 0.05 to 2 wt% in a solvent mixed with distilled water and ethanol in a volume ratio of 4:1 to 5:5.

[0044] The method for manufacturing an anodic oxidation membrane by high-voltage application anodic oxidation according to the present invention

[0045] v) a third anodizing step of forming a third anodic oxide layer by immersing the aluminum substrate having the second anodic oxide layer formed thereon in a sulfuric acid solution, and then performing anodic oxidation while maintaining the temperature of the sulfuric acid solution at -5°C to -2°C and sequentially increasing the applied voltage from 10V to 195V to 200V; and

[0046] vi) a second etching step for removing the third anodic oxide layer generated in the third anodizing step to separate the second anodic oxide layer from the aluminum substrate; further characterized by including

[0047] In the method for manufacturing an anodic oxidation membrane by high voltage application anodic oxidation according to the present invention, v) in the third anodizing step, the current limit is 0.2 to 1 A, and the anodizing is performed.

[0048] In the method for manufacturing an anodic oxidation membrane by high voltage application anodic oxidation according to the present invention, the concentration of the sulfuric acid solution in the v) third anodizing step is 60 wt% to 98 wt%.

[0049] In the method for manufacturing an anodic oxidation membrane by high-voltage application anodic oxidation according to the present invention, the vi) second etching step is characterized by immersing the aluminum substrate on which the second anodic oxidation layer and the third anodic oxidation layer are formed in a phosphoric acid solution having a concentration of 4 wt% to 8 wt% at 30°C to 50°C for 2 minutes to 2 hours.

[0050] The method for manufacturing an anodic oxidation membrane by high-voltage application anodic oxidation according to the present invention is characterized by further comprising: vii) a step of expanding the pore size of the anodic oxidation membrane.

[0051] In the method for manufacturing an anodic oxidation membrane by applying high voltage anodic oxidation according to the present invention, the step of vii) expanding the pores of the anodic oxidation membrane is characterized by immersing the anodic oxidation membrane in a 4 wt% to 8 wt% phosphoric acid solution at 30°C to 50°C for 2 minutes to 2 hours.

[0052] The present invention also provides an anodic oxidation membrane manufactured by the method of manufacturing an anodic oxidation membrane by high voltage application anodic oxidation of the present invention.

[0053] The anodic oxidation membrane according to the present invention is characterized by having a pore size of 150 nm or more and a pore distance of 400 nm or more.

[0054] The anodic oxidation membrane according to the present invention is characterized by having a pore size of 300 nm or more and a pore distance of 400 nm or more.

[0055] The anodic oxidation membrane according to the present invention is characterized in that the anodic oxidation membrane has a diameter of 100 mm * 100 mm or more and a thickness of 10 μm or more.

[0056]

[0057] The method for manufacturing an anodic oxidation membrane according to the present invention applies a voltage of 195V or higher during the first anodizing and second anodizing, and then gradually increases the voltage to 195V so that even when a high voltage of 195V or higher is applied, stable anodizing is possible without the phenomenon of the aluminum surface burning during the anodizing process.

[0058] In addition, the anodic oxidation membrane produced by the manufacturing method according to the present invention can be manufactured over a large area with a pore size of 130 nm or more, preferably 300 nm or more, and a pore distance of 400 nm or more, and a side length of 100 mm or more, as high voltage is stably applied to a large area.

[0059]

[0060] FIG. 1 shows an aluminum substrate on which a first anodizing process has been performed, manufactured according to an embodiment of the present invention.

[0061] FIG. 2 shows an aluminum substrate that has undergone a second anodizing process manufactured according to an embodiment of the present invention.

[0062] FIG. 3 shows an aluminum substrate that has been processed up to the first anodizing step according to a comparative example of the present invention.

[0063] FIG. 4 shows an aluminum substrate that has been subjected to a second anodizing step according to a comparative example of the present invention.

[0064] Figure 5 shows an anodic oxidation membrane manufactured according to an example of the present invention.

[0065] Figures 6 and 7 show the SEM measurement results of an anodic oxidation membrane manufactured according to an embodiment of the present invention.

[0066] Figure 8 shows the SEM measurement results of an anodic oxidation membrane prepared according to a comparative example of the present invention.

[0067] FIG. 9 shows an aluminum substrate that has been subjected to the second anodizing step in an embodiment of the present invention.

[0068] FIG. 10 shows an anodic oxidation membrane manufactured according to an example of the present invention.

[0069] Figures 11 and 12 show the SEM measurement results of an anodic oxidation membrane manufactured according to an embodiment of the present invention.

[0070]

[0071] The present invention will be explained in more detail below through examples. However, the present invention is not limited by the following examples.

[0072]

[0073] <Example 1>

[0074] <Example 1-1> Pretreatment of an aluminum substrate by electrolytic polishing

[0075] Electropolishing was performed on a 99.999% pure aluminum plate with dimensions of 100mm * 100mm and a thickness of 1mm.

[0076] A titanium mesh coated with platinum was used as the counter electrode of an aluminum plate and immersed in a perchloric acid + ethanol mixed solution (volume ratio 1:3), and electrolytic polishing was performed for 240 seconds at 0°C under constant voltage of 20V and current limit of 41A.

[0077] Afterwards, the aluminum plate was washed in distilled water.

[0078]

[0079] <Example 1-2> Primary Anodic Oxidation

[0080] A primary anodic oxidation was performed using the aluminum substrate electropolished in Example 1-1 above by mixing phosphoric acid to a concentration of 0.05 wt% in a solvent mixed with distilled water and ethanol (volume ratio 4:1).

[0081] Anodic oxidation was performed in a 60L anodizing reactor using a solution of 0.05 wt% phosphoric acid mixed into a solvent of distilled water + ethanol (volume ratio 4:1) as the electrolyte, with a graphite plate as the counter electrode, while maintaining -4℃ to -5℃ under constant voltage conditions.

[0082] At this time, the voltage boosting profile configuration in the primary anodic oxidation is as follows.

[0083] Step 1: Applied voltage 10V, current limit 0.5A, hold time 60 seconds,

[0084] In steps 2 through 16, the current was limited to 0.5A, and the voltage was increased by 10V at a time with a holding time of 60 seconds, and the voltage was increased sequentially up to 170V.

[0085] In Step 17, anodic oxidation was performed with a current limit of 0.5A and a voltage increase of 170V for a holding time of 30 seconds, and in Step 18, anodic oxidation was performed with the applied voltage increased by 5V to 175V and a current limit of 0.5A for a holding time of 3 hours.

[0086] Afterwards, the voltage was increased from 175V to 195V by increasing it by 1V at a time with a current limit of 0.5A and maintaining it for 6 seconds.

[0087] After being boosted to 195V, anodic oxidation was performed while maintaining a current limit of 0.5A for 15 hours.

[0088] Figure 1 shows a photograph of an aluminum substrate after the first anodic oxidation was completed by performing anodic oxidation while increasing the applied voltage as described above.

[0089]

[0090] <Examples 1-3> Etching of the primary anodic oxidation membrane

[0091] After washing the aluminum substrate obtained through the above first anodic oxidation process with distilled water, the aluminum substrate was immersed for 4 hours in a mixed solution of chromic acid (2 wt%) and phosphoric acid (6 wt%) while maintaining the temperature at 70°C to etch and remove the anodic oxidation layer formed by the first anodic oxidation in Examples 1-2, and a regular arrangement of seeds was formed on the aluminum substrate.

[0092]

[0093] <Examples 1-4> Secondary Anodic Oxidation

[0094] After the above first anodic oxidation, the aluminum substrate, on which a seed layer was formed on the aluminum surface by etching to remove the first anodic oxidation layer, was washed with distilled water.

[0095] Subsequently, secondary anodic oxidation was performed in the same solution as in the above example.

[0096] At this time, the boost profile configuration used is

[0097] In Step 1, anodizing was performed while maintaining an applied voltage of 10V, a current limit of 0.5A, and a holding time of 60 seconds. Then, 18 steps were performed by increasing the voltage to 10V once and then performing anodizing for a holding time of 60 seconds, thereby sequentially increasing the applied voltage to 190V.

[0098] In Step 19, anodizing was performed with an applied voltage of 190V, a current limit of 0.5A, and a holding time of 30 seconds, and then in Step 20, secondary anodic oxidation was performed by increasing the applied voltage by 5V to 195V and maintaining the current limit of 0.5A for a holding time of 15 hours.

[0099] As such, an aluminum substrate that has undergone a second anodizing step according to an embodiment of the present invention is shown in FIG. 2. As can be seen in FIG. 2, it can be confirmed that the aluminum substrate manufactured in this embodiment has a smooth surface and no burning occurs.

[0100]

[0101] <Comparative Example 1>

[0102] The same aluminum substrate, electrolyte solution, and electrode as in Example 1 above were used, but the applied voltage was different as follows to perform the first anodizing.

[0103] With a voltage step-up profile, Step 1 started with an applied voltage of 10V, a current limit of 0.5A, and a holding time of 60 seconds, and continued for 18 steps with a voltage step-up of 10V followed by a holding time of 60 seconds, thereby increasing the voltage to 190V to perform primary anodic oxidation. That is, in Comparative Example 1, unlike in Example 1 above, anodizing was performed by continuously increasing the voltage from 170V without a separate holding time during the process of increasing the voltage to 190V.

[0104] An aluminum substrate subjected to anodic oxidation according to Comparative Example 1 is shown in FIG. 3. As seen in FIG. 3, the aluminum substrate prepared in the present comparative example did not exhibit surface burning up to 170V, but surface burning occurred as the voltage was increased above 170V, and consequently, subsequent etching and secondary anodic oxidation processes could not be performed.

[0105]

[0106] <Comparative Example 2>

[0107] Using the same electrolyte solution and electrode as in Example 1 above, a first anodic oxidation was performed using the same boosting process, and after removing the first anodic oxidation layer by first etching, a second anodic oxidation was performed.

[0108] In the step-up profile, the voltage was increased to 170V by performing a step-up process in 16 steps, starting with an applied voltage of 10V, a current limit of 0.5A, and a holding time of 60 seconds, and then increasing the voltage to 10V and holding for 60 seconds to perform secondary anodic oxidation.

[0109] That is, in Comparative Example 2, unlike in Example 1 above, the second anodic oxidation was performed with the final applied voltage in the second anodic oxidation set to 170V.

[0110] An aluminum substrate subjected to anodic oxidation according to Comparative Example 2 is shown in FIG. 4. As can be seen in FIG. 4, it can be confirmed that no burning occurs on the surface of the aluminum substrate manufactured in the Comparative Example of the present invention in the case of Comparative Example 2, where up to 170V is applied.

[0111]

[0112] <Example 2> Tertiary Anodic Oxidation

[0113] The aluminum substrate that was secondarily anodized in Examples 1-4 above was immersed in an 18M sulfuric acid solution, and a third anodization was performed while applying voltage with the following step-up profile.

[0114] In Step 1, anodizing was performed with an applied voltage of 10V, a current limit of 0.5A, and a holding time of 60 seconds. Then, 18 steps were performed by sequentially increasing the voltage to 190V by increasing the voltage to 10V and performing anodizing for a holding time of 60 seconds.

[0115] In Step 19, anodizing was performed with an applied voltage of 190V, a current limit of 0.5A, and a holding time of 30 seconds, and then in Step 20, a third anodic oxidation was performed with an applied voltage of 195V, a current limit of 0.5A, and a holding time of 1 hour, thereby forming a third anodic oxidation layer, a sulfuric acid anodic oxidation layer, on the lower part of the second anodic oxidation layer formed in Example 1 by the third anodic oxidation.

[0116]

[0117] <Example 3> Separation of the anodic oxidation membrane

[0118] After washing the aluminum substrate obtained in Example 2 above with distilled water, it was immersed in a 6 wt% phosphoric acid solution at 40°C for 5 minutes, and the sulfuric acid anodic oxide layer formed between the aluminum substrate and the second anodic oxide layer in the third anodic oxidation process was removed by etching, thereby separating the aluminum substrate and the second anodic oxide layer.

[0119] The manufactured anodic oxidation membrane was separated from the aluminum substrate, and the membrane sample separated from the aluminum substrate was washed with distilled water and dried to produce a membrane as shown in Fig. 5.

[0120]

[0121] <Experimental Example> SEM Photo Measurement

[0122] The anodized membrane prepared in Example 3 above was measured by SEM, and the results are shown in Figures 6 and 7, respectively.

[0123] As shown in FIGS. 6 and 7, an anodic oxidation membrane having through holes with a pore size of 130 nm or more was obtained by an embodiment of the present invention.

[0124] As shown in FIGS. 6 and 7, in Example 1 of the present invention, when anodizing is performed while maintaining the voltage at 170V for a certain period of time during the voltage boosting process and then boosting the final applied voltage to 190V or higher, it can be seen that the manufactured membrane is formed with a pore size of 100 nm or more and pores of 130 nm or more arranged with a high degree of alignment.

[0125] In addition, as seen in the SEM image of Fig. 8, when first and second anodizing are performed with the final applied voltage set to 170V in Comparative Example 2, it can be confirmed that although no burning occurs on the surface, a nanostructure with very low pore alignment is formed.

[0126]

[0127] <Example 4>

[0128] <Example 4-1> Pretreatment by Electrolytic Polishing

[0129] To perform anodic oxidation on a large area, a 99.999% pure aluminum plate with dimensions of 220 mm * 240 mm and a thickness of 6 mm was prepared, and electrolytic polishing was performed.

[0130] A platinum-coated titanium mesh was used as the counter electrode of an aluminum plate and immersed in a perchloric acid + ethanol mixed solution (volume ratio 1:3), and electrolytic polishing was performed for 600 seconds at 0°C under constant voltage of 20V and current limit of 80A.

[0131] Afterwards, the aluminum plate was washed in distilled water.

[0132]

[0133] <Example 4-2> Primary Anodic Oxidation

[0134] A primary anodic oxidation was performed using an aluminum substrate electropolished in the above example by mixing phosphoric acid to a solvent mixed with distilled water and ethanol (volume ratio 4:1 to 5:5) to a concentration of 0.5 wt%.

[0135] Anodic oxidation was performed in a 300L PVC tank using a solution of 0.5 wt% phosphoric acid mixed into the solvent of distilled water + ethanol (volume ratio 4:1) as the electrolyte, and a graphite plate as the counter electrode while maintaining -4℃ to -5℃ under constant voltage conditions.

[0136] At this time, the voltage boosting profile configuration in the primary anodic oxidation is as follows.

[0137] Step 1: Perform anodizing at an applied voltage of 10V, a current limit of 1A, and a holding time of 60 seconds, and

[0138] In steps 2 through 16, the current was limited to 1A, and the voltage was increased by 10V at a time and maintained for 60 seconds, and then the voltage was increased to 170V by performing anodizing while increasing the voltage.

[0139] In Step 17, the voltage was increased to 170V with a current limit of 1A and a holding time of 30 seconds, and in Step 18, the applied voltage was increased by 5V to 175V with a current limit of 1A and a holding time of 3 hours.

[0140] Afterwards, the voltage was maintained at a current limit of 1A for 6 seconds, and then increased from 175V to 195V by increasing the voltage by 1V at a time.

[0141] After being boosted to 195V, primary anodic oxidation was performed for 15 hours while maintaining a final applied voltage of 195V and a current limit of 1A.

[0142] A photograph of an aluminum substrate after the first anodic oxidation is shown in Fig. 8. As can be seen in Fig. 8, it can be confirmed that the surface of the anodicated aluminum substrate manufactured according to the embodiment of the present invention is smooth and no burning phenomenon occurs, even though the size is 220 mm * 240 mm.

[0143]

[0144] <Example 4-3> Etching of the primary anodic oxidation membrane

[0145] After washing the aluminum substrate sample obtained through the above first anodic oxidation process with distilled water, the sample was immersed for 4 hours in a mixed solution of chromic acid (1.8 wt%) and phosphoric acid (6 wt%) while maintaining the temperature at 70°C to remove the first anodic oxidation layer formed by the first anodic oxidation by etching, and a regular arrangement of seeds was formed on the surface of the aluminum substrate.

[0146]

[0147] <Example 4-4> Secondary Anodic Oxidation

[0148] The aluminum substrate sample with the above-mentioned regular seeds formed was washed in distilled water.

[0149] Afterwards, secondary anodic oxidation was performed while varying the applied voltage in the step-up process below.

[0150] The boost profile configuration used is

[0151] Step 1: Anodizing was performed with an applied voltage of 10V, a current limit of 1A, and a holding time of 60 seconds, and then anodizing was performed with a voltage increase of 10V once and a holding time of 60 seconds. This method was performed 18 times to increase the applied voltage to 190V.

[0152] In Step 19, anodizing was performed with an applied voltage of 190V, a current limit of 1A, and a holding time of 30 seconds, and then in Step 20, anodizing was performed with the applied voltage increased by 5V to 195V and a current limit of 1A for a holding time of 15 hours.

[0153] As such, an aluminum substrate that has undergone secondary anodic oxidation according to an embodiment of the present invention is shown in FIG. 9. As can be seen in FIG. 9, it can be confirmed that the aluminum substrate that has undergone secondary anodic oxidation manufactured in this embodiment has a smooth surface and no burning occurs.

[0154]

[0155] <Examples 4-5> Tertiary Anodic Oxidation

[0156] The aluminum substrate that was secondarily anodized in Example 4-4 above was immersed in an 18M sulfuric acid solution, and third anodization was performed while applying voltage with the following step-up profile.

[0157] In Step 1, anodizing was performed with an applied voltage of 10V, a current limit of 0.5A, and a holding time of 60 seconds. Then, 18 steps were performed by sequentially increasing the voltage to 190V by increasing the voltage to 10V and performing anodizing for a holding time of 60 seconds.

[0158] In Step 19, anodizing was performed with an applied voltage of 190V, a current limit of 0.5A, and a holding time of 30 seconds, and in Step 20, anodizing was performed with an applied voltage of 190V, a current limit of 0.5A, and a holding time of 30 seconds, and in Step 21, a third anodic oxidation was performed by increasing the applied voltage to 195V by 5V, with a current limit of 0.5A and a holding time of 1 hour, thereby forming a sulfuric acid anodic oxidation layer, which is a third anodic oxidation layer, on the lower part of the second anodic oxidation layer formed in Example 4-1 by the third anodic oxidation.

[0159]

[0160] <Example 4-6> Separation of Anodic Oxidation Membrane

[0161] After washing the aluminum substrate obtained in Examples 4-5 above with distilled water, it was immersed in a 6 wt% phosphoric acid solution at 40°C for 5 minutes to remove the sulfuric acid anodic oxidation layer formed between the aluminum substrate and the second anodic oxidation layer in the third anodic oxidation process by etching, thereby separating the aluminum substrate and the second anodic oxidation layer.

[0162] The manufactured anodic oxidation membrane was separated from the aluminum substrate, and the membrane sample separated from the aluminum substrate was washed with distilled water and dried to produce a membrane as shown in Fig. 10.

[0163]

[0164] <Example 4-7> Pore expansion of an anodic oxidation membrane

[0165] The anodic oxidation membrane separated from the aluminum substrate obtained in Examples 4-6 above was immersed in a 6 wt% phosphoric acid solution at 30°C to expand the pores of the generated anodic oxidation membrane.

[0166]

[0167] <Experimental Example> SEM Photo Measurement

[0168] The pore-expanded anodic oxidized membranes prepared in Examples 4-7 above were measured using SEM, and the results are shown in Figures 11 and 12, respectively.

[0169] As shown in FIGS. 11 and 12, an anodic oxidation membrane was obtained by an embodiment of the present invention having a high degree of pore alignment and through holes with a pore size expanded to 300 nm or more.

[0170]

[0171] The anodic oxidation membrane produced by the manufacturing method according to the present invention can be manufactured as a large-area membrane with a pore size of 130 nm or more, preferably 300 nm or more, and a pore spacing of 400 nm or more, and a side length of 100 mm or more, as a high voltage is stably applied to a large area, thus having high industrial applicability in various fields such as filters and capacitors.

Claims

1. i) A step of preparing an aluminum substrate, wherein an aluminum substrate is prepared; ii) a first anodizing step of immersing the aluminum substrate in a solution containing phosphoric acid, maintaining the temperature of the solution containing phosphoric acid at -5°C to -2°C, and performing anodic oxidation while increasing the applied voltage from 10V to 195V to 200V to form a first anodic oxidation layer on the aluminum substrate; iii) a first etching step for removing a first anodic oxide layer formed on the surface of the aluminum substrate; and iv) a second anodizing step comprising immersing the aluminum substrate from which the first anodic oxide layer has been removed in a solution containing phosphoric acid, maintaining the temperature of the solution containing phosphoric acid at -5°C to -2°C, and performing anodic oxidation while increasing the applied voltage from 10V to 195V to 200V to form a second anodic oxide layer on the aluminum substrate; Method for manufacturing an anodic oxidation membrane by high voltage application anodic oxidation.

2. In Paragraph 1, The above first anodizing step A 1-1 step-up step of performing anodizing while stepping up the applied voltage from 10V to 170V; A first-second step-up stage for performing anodizing while increasing the applied voltage from 170V to 175V; A first-third step-up step of performing anodizing while increasing the applied voltage from 175V to 195V to 200V; and A first-to-fourth step-up step of performing anodizing while maintaining the applied voltage at 195V to 200V; comprising, In the above 1-1 boosting step Anodizing is performed by maintaining an applied voltage of 10V and a current limit of 0.5A for 60 seconds, and then the applied voltage is gradually increased at a rate of 10V / 1 time, and anodizing is performed by maintaining the increased voltage for 60 seconds, thereby sequentially increasing the applied voltage up to 170V. In the above 1st-2nd boosting stage After performing anodizing at a boosted voltage of 170V while maintaining a current limit of 0.5A for 30 seconds, the applied voltage is then boosted by 5V to 175V, and anodizing is performed while maintaining the boosted voltage for 3 hours. In the above 1st-3rd boosting stages Set the current limit to 0.5A, increase the applied voltage from 170V to 195V or 200V at a rate of 1V / 1 cycle, and perform anodizing while maintaining the increased voltage for 6 seconds. In the above 1st-4th boosting steps Performing anodizing for 15 hours while maintaining an applied voltage of 195V to 200V and a current limit of 0.5A. Method for manufacturing an anodic oxidation membrane by high voltage application anodic oxidation.

3. In Paragraph 1, The above second anodizing step 2-1 step-up, which performs anodizing while stepping up the applied voltage from 10V to 190V; A 2-2 step-up step of performing anodizing while increasing the applied voltage from 190V to 195 to 200V; and A second-third step-up step of performing anodizing while maintaining an applied voltage of 195 to 200V; comprising, In the above 2-1 boosting step Anodizing is performed by maintaining the voltage for 60 seconds at an applied voltage of 10V and a current limit of 0.5A, and then anodizing is performed by increasing the voltage at a rate of 10V / 1 time and maintaining the increased voltage for 60 seconds, thereby performing anodizing while sequentially increasing the applied voltage up to 190V. In the above 2-2 boosting step Perform anodizing while maintaining the voltage at an applied voltage of 190V and a current limit of 0.5A for 30 seconds, and thereafter, increase the applied voltage by 5V in one step with a current limit of 0.5A to 195V to 200V, and perform anodizing while maintaining the increased voltage for 30 seconds. In the above 2nd-3rd boosting stage Performing anodizing while maintaining a final applied voltage of 195V to 200V and a current limit of 0.5A for 15 hours Method for manufacturing an anodic oxidation membrane by high voltage application anodic oxidation.

4. In Paragraph 1, The above solution containing phosphoric acid is prepared by mixing distilled water and ethanol in a volume ratio of 4:1 to 5:5 in a solvent, and maintaining the concentration of phosphoric acid at 0.05 to 2 wt%. Method for manufacturing an anodic oxidation membrane by high voltage application anodic oxidation.

5. In Paragraph 1, v) a third anodizing step of forming a third anodic oxide layer by immersing the aluminum substrate having the second anodic oxide layer formed thereon in a sulfuric acid solution, and then performing anodic oxidation while maintaining the temperature of the sulfuric acid solution at -5°C to -2°C and sequentially increasing the applied voltage from 10V to 195V to 200V; and vi) a second etching step for removing the third anodic oxide layer generated in the third anodizing step to separate the second anodic oxide layer from the aluminum substrate; further comprising Method for manufacturing an anodic oxidation membrane by high-voltage application anodic oxidation 6. In Paragraph 5, v) In the third anodizing step above, the current limit is 0.2 to 1 A, and the anodizing is performed. Method for manufacturing an anodic oxidation membrane by high-voltage application anodic oxidation 7. In Paragraph 5, The concentration of the sulfuric acid solution in the above v) third anodizing step is 60 wt% to 98 wt%. Method for manufacturing an anodic oxidation membrane by high-voltage application anodic oxidation 8. In Paragraph 5, In the above vi) second etching step, The aluminum substrate having the second anodic oxide layer and the third anodic oxide layer formed thereon is immersed in a phosphoric acid solution having a concentration of 4 wt% to 8 wt% at 30°C to 50°C for 2 minutes to 2 hours. Method for manufacturing an anodic oxidation membrane by high-voltage application anodic oxidation 9. In Paragraph 5, vii) a step of expanding the pores of the anodic oxidation membrane; further comprising Method for manufacturing an anodic oxidation membrane by high-voltage application anodic oxidation 10. In Paragraph 9, In the step of expanding the pores of the anodic oxidation membrane vii) above, Immersing the anodic oxidation membrane in a 4 wt% to 8 wt% phosphoric acid solution at 30°C to 50°C for 2 minutes to 2 hours Method for manufacturing an anodic oxidation membrane by high-voltage application anodic oxidation 11. An anodic oxidation membrane manufactured by the manufacturing method of claims 1 to 10 12. In Paragraph 11, The above anodic oxidation membrane has a pore size of 150 nm or more and an interpore distance of 400 nm or more. anodic oxidation membrane 13. In Paragraph 11, The above anodic oxidation membrane has a pore size of 300 nm or more and an interpore distance of 400 nm or more. anodic oxidation membrane 14. In Paragraph 11, The above anodic oxidation membrane is 100 mm * 100 mm or larger and has a thickness of 10 μm or larger. anodic oxidation membrane

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