Anodizing apparatus and anodizing method therefor

Abstract

Provided is an anodizing apparatus and an anodizing method therefor capable of efficiently forming an anodic oxide film on a treatment surface of a substrate by using an electrolyte membrane. An anodizing apparatus is an apparatus that applies voltage between a cathode and a substrate to perform an anodizing process on the treatment surface of the substrate. The anodizing apparatus includes a container having an opening covered by an electrolyte membrane; a cathode disposed inside of the container; a power supply that applies voltage between the cathode and the substrate; and a mount base on which the substrate is placed. The electrolyte membrane has a contact region that contacts the substrate and a peripheral region that faces the mount base so as to surround the contact region. A surface of the mount base facing the peripheral region is made of insulating material.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority from Japanese patent application JP 2025-055989 filed on Mar. 28, 2025, the entire content of which is hereby incorporated by reference into this application.BACKGROUNDTechnical Field

[0002] The present disclosure relates to an anodizing apparatus and an anodizing method therefor.Background Art

[0003] Conventionally, a film forming apparatus for forming a metal film on a substrate is known. This film forming apparatus includes a container that contains a plating solution. Inside the container, an anode (electrode) is housed together with a plating solution. The container has an opening formed at a position facing the substrate. The opening is covered by an electrolyte membrane. This allows the plating solution to be sealed inside of the container. At the time of film formation, the electrolyte membrane is first brought into contact with the substrate. Next, voltage is applied between the anode and the substrate. As a result, metal ions contained in the electrolyte membrane are reduced. Consequently, a metal film is formed on the surface of the substrate.SUMMARY

[0004] Meanwhile, a technique for anodizing a substrate is generally known. When an anodizing process is performed using a film forming apparatus described in for example JP 6056987 B, an electrode housed in the container may be used as a cathode and the substrate may be used as an anode.

[0005] However, unlike forming a metal film, the anodizing process forms an oxide film by oxidizing a treatment surface of the substrate, causing the treatment surface of the substrate to have a higher resistance. Therefore, the voltage to be applied across the electrodes need be higher than the voltage at the time of forming a metal film. When the anodizing process is performed, an electrolyte membrane having come into contact with an electrolytic solution contains water, and it is thus assumed that current will flow in a peripheral region of the electrolyte membrane that has not come into contact with the treatment surface of the substrate. Consequently, it may be difficult to efficiently form an anodic oxide film on the treatment surface of the substrate.

[0006] The present disclosure has been made in view of the foregoing, and provides an anodizing apparatus and an anodizing method therefor capable of efficiently forming an anodic oxide film on a treatment surface of a substrate by using an electrolyte membrane.

[0007] In view of the foregoing, an anodizing apparatus according to the present disclosure is a treatment apparatus that applies voltage between a cathode and a substrate to perform an anodizing process on a treatment surface of the substrate. The anodizing apparatus includes: a container having an opening at a position facing the substrate, the opening covered by an electrolyte membrane with an electrolytic solution contained in the container; a cathode disposed inside of the container at a position facing the electrolyte membrane; a power supply that applies voltage between the cathode and the substrate; and a mount base on which the substrate is placed, the mount base being disposed at a position facing the cathode with the electrolyte membrane interposed therebetween. The electrolyte membrane has a contact region that contacts the treatment surface of the substrate and a peripheral region that faces the mount base so as to surround the contact region. A surface of the mount base facing the peripheral region is made of insulating material.

[0008] In some embodiments, the mount base may be made of the insulating material, and a conducting member may be embedded in the mount base, the conducting member allowing a contact surface of the substrate that contacts the mount base to be conductive to a positive electrode of the power supply. In some embodiments, the mount base may have a housing recess for housing the substrate while the substrate is placed thereon, and the mount base may be provided with a suction passage that is continuous with a space formed between a side wall surface of the housing recess and a side surface of the substrate and sucks a fluid in the space.

[0009] In some embodiments, the mount base may include a base body that is made of conductive material and is conductive to a positive electrode of the power supply, and a frame attached to the base body and made of the insulating material facing the peripheral region.

[0010] Furthermore, an anodizing method using these anodizing apparatuses includes first drying a treatment surface of the substrate, then placing the substrate on the mount base. Next, bringing the contact region of the electrolyte membrane into contact with the treatment surface of the substrate and applying voltage of the power supply between the substrate and the cathode to form an anodic oxide film on a surface layer including the treatment surface of the substrate.

[0011] According to the present disclosure, an anodic oxide film can be efficiently formed on a treatment surface of a substrate by using an electrolyte membrane.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1A is a schematic diagram of a treatment apparatus for performing an anodizing method according to a first embodiment;

[0013] FIG. 1B is a schematic plan view showing the positional relation of a mount base and a substrate with respect to an electrolyte membrane of the treatment apparatus shown in FIG. 1A;

[0014] FIG. 2A is a schematic diagram for describing the anodizing method using the treatment apparatus shown in FIG. 1A;

[0015] FIG. 2B is an enlarged view of an X portion of FIG. 2A;

[0016] FIG. 2C is a schematic enlarged perspective view of a substrate after an anodizing process;

[0017] FIG. 3A is a schematic diagram of a treatment apparatus for performing an anodizing method according to a second embodiment;

[0018] FIG. 3B is a schematic plan view showing the positional relation among an electrolyte membrane, a substrate, and a base body with respect to a frame shown in FIG. 3A;

[0019] FIG. 4A is a schematic diagram for describing the anodizing method using the treatment apparatus shown in FIG. 3A;

[0020] FIG. 4B is an enlarged view of an X portion of FIG. 4A;

[0021] FIG. 5A shows a result obtained in Example by measuring the relationship between a voltage application time and an applied voltage under treatment at a constant current using the treatment apparatus shown in FIG. 1A;

[0022] FIG. 5B shows a result obtained in Example showing the relationship between a voltage application time and a film thickness under treatment at a constant current;

[0023] FIG. 6A is a photograph of a treatment surface of a substrate in Example;

[0024] FIG. 6B is a photograph obtained by observing the treatment surface of the substrate of FIG. 6A with an electron microscope;

[0025] FIG. 6C is a cross-sectional photograph of the substrate in Example; and

[0026] FIG. 6D is a photograph obtained by observing the cross section of the substrate of FIG. 6C with the electron microscope.DETAILED DESCRIPTIONFirst Embodiment

[0027] Hereinafter, a treatment apparatus (anodizing apparatus) 1 that performs an anodizing process according to a first embodiment will be described referring to FIGS. 1A-2C. In the present embodiment, the treatment apparatus 1 includes a cathode 11, an electrolyte membrane 13, and a power supply 14 that applies voltage between the cathode 11 and a substrate B.

[0028] As shown in FIGS. 1A and 2A, the treatment apparatus 1 further includes a container 15 that contains the cathode 11 and an electrolytic solution L and a mount base 40 on which the substrate B is placed. The treatment apparatus 1 further includes a linear actuator 70 for raising and lowering the container 15. The linear actuator 70 raises and lowers the container 15 by linearly moving a rod 72 to allow the electrolyte membrane 13 and the substrate B to come in contact with and separate from each other. The linear actuator 70 has the rod 72 that moves linearly with respect to a body 71. The container 15 is securely fixed to a distal end of the rod 72.

[0029] The cathode 11 is an insoluble cathode that does not dissolve in the electrolytic solution L during the anodizing process. Examples of the cathode 11 may include gold, platinum, iridium oxide, or carbon. The substrate B is not particularly limited as long as an oxide film can be formed on a treatment surface Ba by the anodizing process.

[0030] In the present embodiment, the substrate B is a plate having a treatment surface Ba of a rectangular shape, for example. The substrate B has a contact surface Bb that comes in contact with the mount base 40. The contact surface Bb is a backside of the substrate B located opposite the treatment surface Ba of the substrate B. A side surface Bs is formed between the treatment surface Ba and the contact surface Bb. Examples of the substrate B include a metal material such as aluminum, titanium, or magnesium. The substrate B may be a metallic substrate with a film made of such a metal material formed on a conductive material. As will be described later, when at least the treatment surface Ba is made of aluminum, the anodizing process is alumite treatment (aluminum anodizing). The anodic oxide film formed on the treatment surface Ba of the substrate B is an alumite film (anodized aluminum film).

[0031] The cathode 11 is electrically connected to a negative electrode of the power supply 14. The negative electrode of the power supply 14 is electrically connected to the substrate B via a conducting member 30 embedded in the mount base 40. The electrolytic solution L is an acidic aqueous solution. Examples of the electrolytic solution L include a sulfuric acid solution, an oxalic acid solution, or a phosphoric acid solution.

[0032] The electrolyte membrane 13 is a membrane that can be impregnated with (contain) the electrolytic solution L by being brought into contact with the electrolytic solution L. The electrolyte membrane 13 is a flexible membrane. The material of the electrolyte membrane 13 is not particularly limited as long as electron or hydrogen-ion reacted with the treatment surface Ba of the substrate B can move toward the cathode 11 when voltage is applied by the power supply 14. Examples of the material of the electrolyte membrane 13 may include resin having an ion-exchange function, such as a fluorine-based resin, for example, Nafion (registered trademark) manufactured by Du Pont Corporation. As shown in FIG. 1B, the electrolyte membrane 13 has a contact region 13a that contacts the treatment surface Ba of the substrate B and a peripheral region 13b that faces the mount base 40 (described later) so as to surround the contact region 13a.

[0033] As shown in FIG. 1A, a storage space 15a for storing the electrolytic solution L is formed in the container 15. The cathode 11 is disposed in the storage space 15a of the container 15. The storage space 15a includes an opening 15d on a side closer to the substrate B. The opening 15d of the container 15 is covered by the electrolyte membrane 13, and the electrolyte membrane 13 is detachably fixed to the container 15 by a frame 17. Thus, while the electrolytic solution L is stored in the storage space 15a, the opening 15d of the container 15 is sealed with the electrolyte membrane 13. Further, the cathode 11 is disposed inside of the container 15 at a position facing the electrolyte membrane 13.

[0034] The container 15 includes a supply port 15b for supplying the electrolytic solution L to the storage space 15a and a discharge port 15c for discharging the electrolytic solution L from the storage space 15a. The supply port 15b and the discharge port 15c are formed with the storage space 15a interposed therebetween. The supply port 15b is fluidly connected to a supply pipe 51. The discharge port 15c is fluidly connected to a discharge pipe 52.

[0035] The treatment apparatus 1 includes a tank 55 that stores the electrolytic solution L and a circulation mechanism 50 that circulates the electrolytic solution L between the tank 55 and the container 15. The circulation mechanism 50 includes the supply pipe 51, the discharge pipe 52, a circulation pump 53, and a chiller 54. The supply pipe 51 connects the tank 55 and the container 15 and is provided with the chiller 54 and the circulation pump 53. The discharge pipe 52 connects the tank 55 and the container 15. Note that the chiller 54 is a device that cools the electrolytic solution L. The chiller 54 may be provided in the tank 55 or the discharge pipe 52 as long as the electrolytic solution L can be cooled by the chiller 54.

[0036] As shown in FIG. 2A, in the present embodiment, by driving the circulation pump 53, the electrolytic solution L is sucked from the tank 55 into the supply pipe 51 and pressure-fed from the supply port 15b to the storage space 15a. The electrolytic solution L in the storage space 15a is returned to the tank 55 via the discharge port 15c. When the anodizing process is performed, heat generation occurs on the surface of the substrate B. By circulating the electrolytic solution L cooled by the chiller 54, the electrolytic solution L can act as a coolant for cooling the substrate B and the treatment apparatus 1.

[0037] The mount base 40 is a base on which the substrate B is placed. The mount base 40 is disposed at a position facing the cathode 11 with the electrolyte membrane 13 interposed therebetween. The mount base 40 is made of insulating material. Examples of the material of the mount base 40 include resin or ceramics, but the material of the mount base 40 is not particularly limited as long as the material is electrically insulative.

[0038] Therefore, in the present embodiment, as shown in FIGS. 1B and 2B, a surface 40a of the mount base 40 facing the peripheral region 13b of the electrolyte membrane 13 is made of insulating material. The mount base 40 has a housing recess 40b for housing the substrate B while the substrate B is placed thereon. The housing recess 40b includes a housing space S in which the substrate B is housed. The housing recess 40b has a bottom wall surface 43 that abuts on the contact surface Bb of the substrate B and a side wall surface 41 that faces the side surface Bs of the substrate B.

[0039] The conducting member 30 that allows the contact surface Bb of the substrate B to be conductive to a positive electrode of the power supply 14 is embedded in the mount base 40. Examples of the material of the conducting member 30 include stainless steel or titanium alloy, but the material of the conducting member 30 is not particularly limited as long as the material does not dissolve in the electrolytic solution L and allows the substrate B and the positive electrode of the power supply 14 to be conductive to each other.

[0040] The conducting member 30 includes a first conducting portion 31 and a second conducting portion 32. The first conducting portion 31 is a rod-shaped part connected to the positive electrode of the power supply 14 and inserted into the mount base 40 from the side surface of the mount base 40. The second conducting portion 32 is a pin-shaped part inserted into the mount base 40 from the bottom wall surface 43 of the housing recess 40b and connected to the first conducting portion 31. In the present embodiment, there are two second conducting portions 32, but the number of second conducting portions 32 is not particularly limited.

[0041] An end face 33 of the second conducting portion 32 serves as a part of the bottom wall surface 43 of the housing recess 40b. The end face 33 of the second conducting portion 32 and the bottom wall surface 43 of the housing recess 40b are formed on the same plane. In this manner, housing the substrate B in the housing recess 40b allows the contact surface Bb of the substrate B and the bottom wall surface 43 of the housing recess 40b to come into surface contact with each other. Consequently, the electrolytic solution L is less likely to enter between the contact surface Bb of the substrate B and the bottom wall surface 43 of the housing recess 40b, and thus it is possible to stabilize the current flow between the substrate B and the cathode 11 and stabilize the anodizing process using the treatment surface Ba of the substrate B.

[0042] As shown in FIG. 2B, while the substrate B is housed in the housing recess 40b of the mount base 40, a space C serving as a small gap is formed between the side wall surface 41 of the housing recess 40b and the side surface Bs of the substrate B. The mount base 40 is provided with a suction passage 61 which is continuous with this space C and sucks a fluid (e.g. the electrolytic solution L or air) in the space C. A suction pump 63 is connected to the suction passage 61 via a suction pipe 62.

[0043] In the present embodiment, as shown in FIG. 1B, a plurality of suction ports 61a of the suction passage 61 is provided along an edge portion of the bottom wall surface 43 of the housing recess 40b. Thus, even if the electrolytic solution L enters between the side surface Bs of the substrate B and the side wall surface 41 of the housing recess 40b, the electrolytic solution L can be discharged. This can stably pass the current through the treatment surface Ba of the substrate B. In addition, the substrate B can be adsorbed onto the bottom wall surface 43 of the mount base 40. Consequently, the anodizing process on the treatment surface Ba of the substrate B can be stably performed.

[0044] Hereinafter, an anodizing method using an anodizing apparatus will be described. First, the substrate B is subjected to pretreatment such as cleaning, and then the treatment surface Ba of the substrate B is dried. Specifically, such drying is carried out by air blowing. This drying step can remove water on the treatment surface Ba of the substrate B. Consequently, when performing an anodizing process (described later), it is possible to prevent the current from flowing to other than the treatment surface Ba due to the water flow on the treatment surface Ba of the substrate B. After that, for example, a peripheral edge including the side surface Bs of the substrate B may be coated with resin tape or thin film rubber.

[0045] Next, the substrate B is placed on the mount base 40 by housing the substrate B in the housing recess 40b of the mount base 40. Next, the electrolyte membrane 13 is brought into contact with the substrate B. Specifically, by driving the linear actuator 70, the container 15 securely fixed to the distal end of the rod 72 is moved toward the mount base 40 until the electrolyte membrane 13 abuts on the substrate B (see, for example, FIG. 2A). This allows the contact region 13a of the electrolyte membrane 13 to come into contact with the treatment surface Ba of the substrate B. Further, the peripheral region 13b of the electrolyte membrane 13 can be brought into contact with the surface 40a of the mount base 40 made of insulating material.

[0046] Next, the electrolytic solution L is contained in the container 15. Specifically, by driving the circulation pump 53, the electrolytic solution L is sucked from the tank 55 into the supply pipe 51 and pressure-fed from the supply port 15b to the storage space 15a. The electrolytic solution L in the storage space 15a is returned to the tank 55 via the discharge port 15c. In this way, the electrolytic solution L is circulated through the container 15. Note that only a circulation pressure caused by the circulation pump 53 acts on the electrolytic solution L in the container 15. Therefore, since only the circulation pressure of the electrolytic solution L acts on the substrate B via the electrolyte membrane 13, it is possible to suppress excessive exudation of the electrolytic solution L from the electrolyte membrane 13 to the substrate B.

[0047] In this state, voltage of the power supply 14 is applied between the substrate B and the cathode 11. At the same time, the suction pump 63 is actuated. As a result, as shown in FIG. 2C, an anodic oxide film Bf is formed on a surface layer Bc including the treatment surface Ba of the substrate B. The anodic oxide film Bf includes a plurality of micropores Bh. Thereafter, the electrolytic solution L is drawn from the storage space 15a of the container 15. The linear actuator 70 is driven to separate the electrolyte membrane 13 from the substrate B, and the substrate B is removed from the mount base 40.

[0048] Since the anodic oxide film Bf formed on the substrate B has higher electric resistivity with respect to a base material Bm of the substrate B, current of the power supply 14 hardly flows between the treatment surface Ba of the substrate B and the cathode 11. Therefore, the current easily flows also through the mount base 40 via the peripheral region 13b of the electrolyte membrane 13. However, in the present embodiment, since the mount base 40 is made of insulating material, the surface 40a of the mount base 40 facing the peripheral region 13b is also made of insulating material. As a result, it is possible to prevent the current from flowing through the mount base 40 via the peripheral region 13b of the electrolyte membrane 13, and to efficiently pass the current from the power supply 14 between the treatment surface Ba of the substrate B and the cathode 11.

[0049] Consequently, with the electrolyte membrane, the anodic oxide film Bf can be efficiently formed on the treatment surface Ba of the substrate B. Further, by actuating the suction pump 63, the water contained in the electrolytic solution L exuded from the electrolyte membrane 13 can be released through the suction passage 61. As a result, it is possible to more efficiently pass the current from the power supply 14 between the treatment surface Ba of the substrate B and the cathode 11.Second Embodiment

[0050] Hereinafter, a treatment apparatus (anodizing apparatus) 1 that performs an anodizing process according to a second embodiment will be described referring to a FIGS. 3A-4B. The difference between the present embodiment and the first embodiment is the structure of the mount base 40. Therefore, members and mechanisms identical to those of the first embodiment are denoted by the same reference signs in FIGS. 3A-4B, and detailed description thereof will be omitted.

[0051] As shown in FIG. 3A, a mount base 40 includes a base body 45 that is conductive to the positive electrode of a power supply 14 and a frame 47 attached to the base body 45. The base body 45 is made of conductive material such as stainless steel. Therefore, unlike the mount base of the first embodiment, the base body 45 is not provided with a conducting member 30. Like the mount base of the first embodiment, the base body 45 includes a housing recess 40b for housing a substrate B. Further, as shown in FIGS. 4A and 4B, the base body 45 is provided with a suction passage 61 which is continuous with a space C formed between a side wall surface 41 of the housing recess 40b and a side surface Bs of the substrate B and sucks a fluid in the space C. A suction pump 63 is connected to the suction passage 61 via a suction pipe 62.

[0052] The frame 47 faces a peripheral region 13b of an electrolyte membrane 13. The frame 47 is made of insulating material such as resin or ceramics. As shown in FIG. 3A, the frame 47 includes an opening 47a. The treatment surface Ba of the substrate B is exposed from the opening 47a of the frame 47 while the substrate B is housed in the housing recess 40b of the base body 45. Therefore, the space region surrounded by the opening 47a of the frame 47 faces the contact region 13a of the electrolyte membrane 13, and the frame 47 faces the peripheral region 13b of the electrolyte membrane 13. The surface 40a of the mount base 40 facing the peripheral region 13b of the electrolyte membrane 13 is made of insulating material.

[0053] As shown in FIG. 3B, like the first embodiment, also in the present embodiment, the treatment surface Ba of the substrate B is first dried, and then the substrate B is placed on the mount base 40. At this time, the substrate B may be first housed in the housing recess 40b of the base body 45 and then the frame 47 may be attached. Next, a linear actuator 70 is moved to bring the contact region 13a of the electrolyte membrane 13 into contact with the treatment surface Ba of the substrate B. Next, a circulation pump 53 is driven to supply the electrolytic solution L to the container 15 and circulate the electrolytic solution L. In this state, voltage of the power supply 14 is applied between the substrate B and the cathode 11. At the same time, the suction pump 63 is actuated. Consequently, like the one shown in FIG. 2C, in the present embodiment in which an anodic oxide film Bf can be formed on a surface layer Bc including the treatment surface Ba of the substrate B, during the anodizing process, the surface 40a contacting the peripheral region 13b of the electrolyte membrane 13 is made of insulating material, and thus the same advantageous effect as the first embodiment can be expected.Example

[0054] An anodizing process was performed on the treatment surface Ba of the substrate B using the treatment apparatus shown in FIG. 1A. As the substrate B, 20 sheets of pure aluminum (A1050) were prepared. The size of the treatment surface Ba of the substrate B is 50 mm × 50 mm. The thickness of the substrate B is 0.5 mm. Next, as the electrolytic solution, 10% by weight of aqueous sulfuric acid solution was prepared. As the power supply, a DC power supply (model number ZX-400LA manufactured by Takasago Seisakusho Co., Ltd.) was used. As the cathode, a mesh electrode with an iridium-oxide-coating on the surface was prepared. The mesh diameter of the mesh electrode was 50 mm. 2L of the electrolytic solution was cooled on ice to below 10 °C. Then, voltage was applied between the substrate and the cathode under constant current conditions while circulating the electrolytic solution. The current conditions were a current-density of 1.0 A / dm2 and a current-density of 3 A / dm2. For each current condition, an anodic oxide film was formed for ten substrates.

[0055] FIG. 5A shows a result obtained in Example by measuring the relationship between a voltage application time and an applied voltage under treatment at a constant current (a current-density of 1A / dm2). As shown in FIG. 5A, when the application of the voltage started, the voltage value became higher due to a natural oxide film formed on the treatment surface of the substrate. However, as the application time goes by, the applied voltage stabilized to a substantially constant value (substantially 20 V). When a metal film is formed with the same constant current using the film forming apparatus shown in the background art, the applied voltage is about 5 V. Therefore, the applied voltage during the anodizing process is higher than the applied voltage during metal film formation. This is considered to be because an oxide film is formed on the treatment surface of the substrate when the anodizing process is performed.

[0056] FIG. 5B shows a result obtained in Example showing the relationship between a voltage application time and a film thickness under treatment at a constant current (a current-density of 1 A / dm2 and a current-density of 3 A / dm2). In FIG. 5B, a result obtained by forming an anodic oxide film on the substrate in a bath containing an electrolytic solution is shown by a solid line as a reference example. In view of this result, the result of a current-density of 1 A / dm2 was substantially the same as the result of the reference example. Furthermore, it was found that, when the applied voltage was constant, increasing the current density resulted in faster formation of the anodic oxide film up to a predetermined film thickness. This was because the surface of the mount base facing the peripheral region of the electrolyte membrane was made of insulating material, and thus it was possible to efficiently pass the current between the cathode and the substrate.

[0057] Furthermore, the treatment surface and the cross section of the substrate on which the anodizing process was performed under the condition of a current-density of 3 A / dm2 was observed. The results are shown in FIGS. 6A-6D. FIG. 6A is a photograph of the treatment surface of the substrate in Example. FIG. 6B is a photograph obtained by observing the treatment surface of the substrate of FIG. 6A with an electron microscope. FIG. 6C is a cross-sectional photograph of the substrate in Example. FIG. 6D is a photograph obtained by observing the cross section of the substrate of FIG. 6C with the electron microscope.

[0058] As can be seen in FIG. 6C, the surface layer including the treatment surface of the substrate is an alumite film (anodic oxide film). Further, as shown in FIGS. 6B and 6D, micropores unique to the alumite film were formed on the treatment surface of the substrate on which the anodizing process was performed.

[0059] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above-described embodiments, and various design changes can be made within the scope without departing from the spirit of the present disclosure described in the claims.

[0060] In the second embodiment, the frame made of insulating material was attached to the base body made of conductive material. However, for example, a surface of the base body that contacts the peripheral region of the electrolyte membrane may be coated with conductive material such as resin.

Examples

first embodiment

[0027]Hereinafter, a treatment apparatus (anodizing apparatus) 1 that performs an anodizing process according to a first embodiment will be described referring to FIGS. 1A-2C. In the present embodiment, the treatment apparatus 1 includes a cathode 11, an electrolyte membrane 13, and a power supply 14 that applies voltage between the cathode 11 and a substrate B.

[0028]As shown in FIGS. 1A and 2A, the treatment apparatus 1 further includes a container 15 that contains the cathode 11 and an electrolytic solution L and a mount base 40 on which the substrate B is placed. The treatment apparatus 1 further includes a linear actuator 70 for raising and lowering the container 15. The linear actuator 70 raises and lowers the container 15 by linearly moving a rod 72 to allow the electrolyte membrane 13 and the substrate B to come in contact with and separate from each other. The linear actuator 70 has the rod 72 that moves linearly with respect to a body 71. The container 15 is securely fixed ...

second embodiment

[0050]Hereinafter, a treatment apparatus (anodizing apparatus) 1 that performs an anodizing process according to a second embodiment will be described referring to a FIGS. 3A-4B. The difference between the present embodiment and the first embodiment is the structure of the mount base 40. Therefore, members and mechanisms identical to those of the first embodiment are denoted by the same reference signs in FIGS. 3A-4B, and detailed description thereof will be omitted.

[0051]As shown in FIG. 3A, a mount base 40 includes a base body 45 that is conductive to the positive electrode of a power supply 14 and a frame 47 attached to the base body 45. The base body 45 is made of conductive material such as stainless steel. Therefore, unlike the mount base of the first embodiment, the base body 45 is not provided with a conducting member 30. Like the mount base of the first embodiment, the base body 45 includes a housing recess 40b for housing a substrate B. Further, as shown in FIGS. 4A and 4B...

example

[0054]An anodizing process was performed on the treatment surface Ba of the substrate B using the treatment apparatus shown in FIG. 1A. As the substrate B, 20 sheets of pure aluminum (A1050) were prepared. The size of the treatment surface Ba of the substrate B is 50 mm × 50 mm. The thickness of the substrate B is 0.5 mm. Next, as the electrolytic solution, 10% by weight of aqueous sulfuric acid solution was prepared. As the power supply, a DC power supply (model number ZX-400LA manufactured by Takasago Seisakusho Co., Ltd.) was used. As the cathode, a mesh electrode with an iridium-oxide-coating on the surface was prepared. The mesh diameter of the mesh electrode was 50 mm. 2L of the electrolytic solution was cooled on ice to below 10 °C. Then, voltage was applied between the substrate and the cathode under constant current conditions while circulating the electrolytic solution. The current conditions were a current-density of 1.0 A / dm2 and a current-density of 3 A / dm2. For each cu...

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority from Japanese patent application JP 2025-055989 filed on Mar. 28, 2025, the entire content of which is hereby incorporated by reference into this application.BACKGROUNDTechnical Field

[0002] The present disclosure relates to an anodizing apparatus and an anodizing method therefor.Background Art

[0003] Conventionally, a film forming apparatus for forming a metal film on a substrate is known. This film forming apparatus includes a container that contains a plating solution. Inside the container, an anode (electrode) is housed together with a plating solution. The container has an opening formed at a position facing the substrate. The opening is covered by an electrolyte membrane. This allows the plating solution to be sealed inside of the container. At the time of film formation, the electrolyte membrane is first brought into contact with the substrate. Next, voltage is applied between the anode and the substrate. As a result, metal ions contained in the electrolyte membrane are reduced. Consequently, a metal film is formed on the surface of the substrate.SUMMARY

[0004] Meanwhile, a technique for anodizing a substrate is generally known. When an anodizing process is performed using a film forming apparatus described in for example JP 6056987 B, an electrode housed in the container may be used as a cathode and the substrate may be used as an anode.

[0005] However, unlike forming a metal film, the anodizing process forms an oxide film by oxidizing a treatment surface of the substrate, causing the treatment surface of the substrate to have a higher resistance. Therefore, the voltage to be applied across the electrodes need be higher than the voltage at the time of forming a metal film. When the anodizing process is performed, an electrolyte membrane having come into contact with an electrolytic solution contains water, and it is thus assumed that current will flow in a peripheral region of the electrolyte membrane that has not come into contact with the treatment surface of the substrate. Consequently, it may be difficult to efficiently form an anodic oxide film on the treatment surface of the substrate.

[0006] The present disclosure has been made in view of the foregoing, and provides an anodizing apparatus and an anodizing method therefor capable of efficiently forming an anodic oxide film on a treatment surface of a substrate by using an electrolyte membrane.

[0007] In view of the foregoing, an anodizing apparatus according to the present disclosure is a treatment apparatus that applies voltage between a cathode and a substrate to perform an anodizing process on a treatment surface of the substrate. The anodizing apparatus includes: a container having an opening at a position facing the substrate, the opening covered by an electrolyte membrane with an electrolytic solution contained in the container; a cathode disposed inside of the container at a position facing the electrolyte membrane; a power supply that applies voltage between the cathode and the substrate; and a mount base on which the substrate is placed, the mount base being disposed at a position facing the cathode with the electrolyte membrane interposed therebetween. The electrolyte membrane has a contact region that contacts the treatment surface of the substrate and a peripheral region that faces the mount base so as to surround the contact region. A surface of the mount base facing the peripheral region is made of insulating material.

[0008] In some embodiments, the mount base may be made of the insulating material, and a conducting member may be embedded in the mount base, the conducting member allowing a contact surface of the substrate that contacts the mount base to be conductive to a positive electrode of the power supply. In some embodiments, the mount base may have a housing recess for housing the substrate while the substrate is placed thereon, and the mount base may be provided with a suction passage that is continuous with a space formed between a side wall surface of the housing recess and a side surface of the substrate and sucks a fluid in the space.

[0009] In some embodiments, the mount base may include a base body that is made of conductive material and is conductive to a positive electrode of the power supply, and a frame attached to the base body and made of the insulating material facing the peripheral region.

[0010] Furthermore, an anodizing method using these anodizing apparatuses includes first drying a treatment surface of the substrate, then placing the substrate on the mount base. Next, bringing the contact region of the electrolyte membrane into contact with the treatment surface of the substrate and applying voltage of the power supply between the substrate and the cathode to form an anodic oxide film on a surface layer including the treatment surface of the substrate.

[0011] According to the present disclosure, an anodic oxide film can be efficiently formed on a treatment surface of a substrate by using an electrolyte membrane.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1A is a schematic diagram of a treatment apparatus for performing an anodizing method according to a first embodiment;

[0013] FIG. 1B is a schematic plan view showing the positional relation of a mount base and a substrate with respect to an electrolyte membrane of the treatment apparatus shown in FIG. 1A;

[0014] FIG. 2A is a schematic diagram for describing the anodizing method using the treatment apparatus shown in FIG. 1A;

[0015] FIG. 2B is an enlarged view of an X portion of FIG. 2A;

[0016] FIG. 2C is a schematic enlarged perspective view of a substrate after an anodizing process;

[0017] FIG. 3A is a schematic diagram of a treatment apparatus for performing an anodizing method according to a second embodiment;

[0018] FIG. 3B is a schematic plan view showing the positional relation among an electrolyte membrane, a substrate, and a base body with respect to a frame shown in FIG. 3A;

[0019] FIG. 4A is a schematic diagram for describing the anodizing method using the treatment apparatus shown in FIG. 3A;

[0020] FIG. 4B is an enlarged view of an X portion of FIG. 4A;

[0021] FIG. 5A shows a result obtained in Example by measuring the relationship between a voltage application time and an applied voltage under treatment at a constant current using the treatment apparatus shown in FIG. 1A;

[0022] FIG. 5B shows a result obtained in Example showing the relationship between a voltage application time and a film thickness under treatment at a constant current;

[0023] FIG. 6A is a photograph of a treatment surface of a substrate in Example;

[0024] FIG. 6B is a photograph obtained by observing the treatment surface of the substrate of FIG. 6A with an electron microscope;

[0025] FIG. 6C is a cross-sectional photograph of the substrate in Example; and

[0026] FIG. 6D is a photograph obtained by observing the cross section of the substrate of FIG. 6C with the electron microscope.DETAILED DESCRIPTIONFirst Embodiment

[0027] Hereinafter, a treatment apparatus (anodizing apparatus) 1 that performs an anodizing process according to a first embodiment will be described referring to FIGS. 1A-2C. In the present embodiment, the treatment apparatus 1 includes a cathode 11, an electrolyte membrane 13, and a power supply 14 that applies voltage between the cathode 11 and a substrate B.

[0028] As shown in FIGS. 1A and 2A, the treatment apparatus 1 further includes a container 15 that contains the cathode 11 and an electrolytic solution L and a mount base 40 on which the substrate B is placed. The treatment apparatus 1 further includes a linear actuator 70 for raising and lowering the container 15. The linear actuator 70 raises and lowers the container 15 by linearly moving a rod 72 to allow the electrolyte membrane 13 and the substrate B to come in contact with and separate from each other. The linear actuator 70 has the rod 72 that moves linearly with respect to a body 71. The container 15 is securely fixed to a distal end of the rod 72.

[0029] The cathode 11 is an insoluble cathode that does not dissolve in the electrolytic solution L during the anodizing process. Examples of the cathode 11 may include gold, platinum, iridium oxide, or carbon. The substrate B is not particularly limited as long as an oxide film can be formed on a treatment surface Ba by the anodizing process.

[0030] In the present embodiment, the substrate B is a plate having a treatment surface Ba of a rectangular shape, for example. The substrate B has a contact surface Bb that comes in contact with the mount base 40. The contact surface Bb is a backside of the substrate B located opposite the treatment surface Ba of the substrate B. A side surface Bs is formed between the treatment surface Ba and the contact surface Bb. Examples of the substrate B include a metal material such as aluminum, titanium, or magnesium. The substrate B may be a metallic substrate with a film made of such a metal material formed on a conductive material. As will be described later, when at least the treatment surface Ba is made of aluminum, the anodizing process is alumite treatment (aluminum anodizing). The anodic oxide film formed on the treatment surface Ba of the substrate B is an alumite film (anodized aluminum film).

[0031] The cathode 11 is electrically connected to a negative electrode of the power supply 14. The negative electrode of the power supply 14 is electrically connected to the substrate B via a conducting member 30 embedded in the mount base 40. The electrolytic solution L is an acidic aqueous solution. Examples of the electrolytic solution L include a sulfuric acid solution, an oxalic acid solution, or a phosphoric acid solution.

[0032] The electrolyte membrane 13 is a membrane that can be impregnated with (contain) the electrolytic solution L by being brought into contact with the electrolytic solution L. The electrolyte membrane 13 is a flexible membrane. The material of the electrolyte membrane 13 is not particularly limited as long as electron or hydrogen-ion reacted with the treatment surface Ba of the substrate B can move toward the cathode 11 when voltage is applied by the power supply 14. Examples of the material of the electrolyte membrane 13 may include resin having an ion-exchange function, such as a fluorine-based resin, for example, Nafion (registered trademark) manufactured by Du Pont Corporation. As shown in FIG. 1B, the electrolyte membrane 13 has a contact region 13a that contacts the treatment surface Ba of the substrate B and a peripheral region 13b that faces the mount base 40 (described later) so as to surround the contact region 13a.

[0033] As shown in FIG. 1A, a storage space 15a for storing the electrolytic solution L is formed in the container 15. The cathode 11 is disposed in the storage space 15a of the container 15. The storage space 15a includes an opening 15d on a side closer to the substrate B. The opening 15d of the container 15 is covered by the electrolyte membrane 13, and the electrolyte membrane 13 is detachably fixed to the container 15 by a frame 17. Thus, while the electrolytic solution L is stored in the storage space 15a, the opening 15d of the container 15 is sealed with the electrolyte membrane 13. Further, the cathode 11 is disposed inside of the container 15 at a position facing the electrolyte membrane 13.

[0034] The container 15 includes a supply port 15b for supplying the electrolytic solution L to the storage space 15a and a discharge port 15c for discharging the electrolytic solution L from the storage space 15a. The supply port 15b and the discharge port 15c are formed with the storage space 15a interposed therebetween. The supply port 15b is fluidly connected to a supply pipe 51. The discharge port 15c is fluidly connected to a discharge pipe 52.

[0035] The treatment apparatus 1 includes a tank 55 that stores the electrolytic solution L and a circulation mechanism 50 that circulates the electrolytic solution L between the tank 55 and the container 15. The circulation mechanism 50 includes the supply pipe 51, the discharge pipe 52, a circulation pump 53, and a chiller 54. The supply pipe 51 connects the tank 55 and the container 15 and is provided with the chiller 54 and the circulation pump 53. The discharge pipe 52 connects the tank 55 and the container 15. Note that the chiller 54 is a device that cools the electrolytic solution L. The chiller 54 may be provided in the tank 55 or the discharge pipe 52 as long as the electrolytic solution L can be cooled by the chiller 54.

[0036] As shown in FIG. 2A, in the present embodiment, by driving the circulation pump 53, the electrolytic solution L is sucked from the tank 55 into the supply pipe 51 and pressure-fed from the supply port 15b to the storage space 15a. The electrolytic solution L in the storage space 15a is returned to the tank 55 via the discharge port 15c. When the anodizing process is performed, heat generation occurs on the surface of the substrate B. By circulating the electrolytic solution L cooled by the chiller 54, the electrolytic solution L can act as a coolant for cooling the substrate B and the treatment apparatus 1.

[0037] The mount base 40 is a base on which the substrate B is placed. The mount base 40 is disposed at a position facing the cathode 11 with the electrolyte membrane 13 interposed therebetween. The mount base 40 is made of insulating material. Examples of the material of the mount base 40 include resin or ceramics, but the material of the mount base 40 is not particularly limited as long as the material is electrically insulative.

[0038] Therefore, in the present embodiment, as shown in FIGS. 1B and 2B, a surface 40a of the mount base 40 facing the peripheral region 13b of the electrolyte membrane 13 is made of insulating material. The mount base 40 has a housing recess 40b for housing the substrate B while the substrate B is placed thereon. The housing recess 40b includes a housing space S in which the substrate B is housed. The housing recess 40b has a bottom wall surface 43 that abuts on the contact surface Bb of the substrate B and a side wall surface 41 that faces the side surface Bs of the substrate B.

[0039] The conducting member 30 that allows the contact surface Bb of the substrate B to be conductive to a positive electrode of the power supply 14 is embedded in the mount base 40. Examples of the material of the conducting member 30 include stainless steel or titanium alloy, but the material of the conducting member 30 is not particularly limited as long as the material does not dissolve in the electrolytic solution L and allows the substrate B and the positive electrode of the power supply 14 to be conductive to each other.

[0040] The conducting member 30 includes a first conducting portion 31 and a second conducting portion 32. The first conducting portion 31 is a rod-shaped part connected to the positive electrode of the power supply 14 and inserted into the mount base 40 from the side surface of the mount base 40. The second conducting portion 32 is a pin-shaped part inserted into the mount base 40 from the bottom wall surface 43 of the housing recess 40b and connected to the first conducting portion 31. In the present embodiment, there are two second conducting portions 32, but the number of second conducting portions 32 is not particularly limited.

[0041] An end face 33 of the second conducting portion 32 serves as a part of the bottom wall surface 43 of the housing recess 40b. The end face 33 of the second conducting portion 32 and the bottom wall surface 43 of the housing recess 40b are formed on the same plane. In this manner, housing the substrate B in the housing recess 40b allows the contact surface Bb of the substrate B and the bottom wall surface 43 of the housing recess 40b to come into surface contact with each other. Consequently, the electrolytic solution L is less likely to enter between the contact surface Bb of the substrate B and the bottom wall surface 43 of the housing recess 40b, and thus it is possible to stabilize the current flow between the substrate B and the cathode 11 and stabilize the anodizing process using the treatment surface Ba of the substrate B.

[0042] As shown in FIG. 2B, while the substrate B is housed in the housing recess 40b of the mount base 40, a space C serving as a small gap is formed between the side wall surface 41 of the housing recess 40b and the side surface Bs of the substrate B. The mount base 40 is provided with a suction passage 61 which is continuous with this space C and sucks a fluid (e.g. the electrolytic solution L or air) in the space C. A suction pump 63 is connected to the suction passage 61 via a suction pipe 62.

[0043] In the present embodiment, as shown in FIG. 1B, a plurality of suction ports 61a of the suction passage 61 is provided along an edge portion of the bottom wall surface 43 of the housing recess 40b. Thus, even if the electrolytic solution L enters between the side surface Bs of the substrate B and the side wall surface 41 of the housing recess 40b, the electrolytic solution L can be discharged. This can stably pass the current through the treatment surface Ba of the substrate B. In addition, the substrate B can be adsorbed onto the bottom wall surface 43 of the mount base 40. Consequently, the anodizing process on the treatment surface Ba of the substrate B can be stably performed.

[0044] Hereinafter, an anodizing method using an anodizing apparatus will be described. First, the substrate B is subjected to pretreatment such as cleaning, and then the treatment surface Ba of the substrate B is dried. Specifically, such drying is carried out by air blowing. This drying step can remove water on the treatment surface Ba of the substrate B. Consequently, when performing an anodizing process (described later), it is possible to prevent the current from flowing to other than the treatment surface Ba due to the water flow on the treatment surface Ba of the substrate B. After that, for example, a peripheral edge including the side surface Bs of the substrate B may be coated with resin tape or thin film rubber.

[0045] Next, the substrate B is placed on the mount base 40 by housing the substrate B in the housing recess 40b of the mount base 40. Next, the electrolyte membrane 13 is brought into contact with the substrate B. Specifically, by driving the linear actuator 70, the container 15 securely fixed to the distal end of the rod 72 is moved toward the mount base 40 until the electrolyte membrane 13 abuts on the substrate B (see, for example, FIG. 2A). This allows the contact region 13a of the electrolyte membrane 13 to come into contact with the treatment surface Ba of the substrate B. Further, the peripheral region 13b of the electrolyte membrane 13 can be brought into contact with the surface 40a of the mount base 40 made of insulating material.

[0046] Next, the electrolytic solution L is contained in the container 15. Specifically, by driving the circulation pump 53, the electrolytic solution L is sucked from the tank 55 into the supply pipe 51 and pressure-fed from the supply port 15b to the storage space 15a. The electrolytic solution L in the storage space 15a is returned to the tank 55 via the discharge port 15c. In this way, the electrolytic solution L is circulated through the container 15. Note that only a circulation pressure caused by the circulation pump 53 acts on the electrolytic solution L in the container 15. Therefore, since only the circulation pressure of the electrolytic solution L acts on the substrate B via the electrolyte membrane 13, it is possible to suppress excessive exudation of the electrolytic solution L from the electrolyte membrane 13 to the substrate B.

[0047] In this state, voltage of the power supply 14 is applied between the substrate B and the cathode 11. At the same time, the suction pump 63 is actuated. As a result, as shown in FIG. 2C, an anodic oxide film Bf is formed on a surface layer Bc including the treatment surface Ba of the substrate B. The anodic oxide film Bf includes a plurality of micropores Bh. Thereafter, the electrolytic solution L is drawn from the storage space 15a of the container 15. The linear actuator 70 is driven to separate the electrolyte membrane 13 from the substrate B, and the substrate B is removed from the mount base 40.

[0048] Since the anodic oxide film Bf formed on the substrate B has higher electric resistivity with respect to a base material Bm of the substrate B, current of the power supply 14 hardly flows between the treatment surface Ba of the substrate B and the cathode 11. Therefore, the current easily flows also through the mount base 40 via the peripheral region 13b of the electrolyte membrane 13. However, in the present embodiment, since the mount base 40 is made of insulating material, the surface 40a of the mount base 40 facing the peripheral region 13b is also made of insulating material. As a result, it is possible to prevent the current from flowing through the mount base 40 via the peripheral region 13b of the electrolyte membrane 13, and to efficiently pass the current from the power supply 14 between the treatment surface Ba of the substrate B and the cathode 11.

[0049] Consequently, with the electrolyte membrane, the anodic oxide film Bf can be efficiently formed on the treatment surface Ba of the substrate B. Further, by actuating the suction pump 63, the water contained in the electrolytic solution L exuded from the electrolyte membrane 13 can be released through the suction passage 61. As a result, it is possible to more efficiently pass the current from the power supply 14 between the treatment surface Ba of the substrate B and the cathode 11.Second Embodiment

[0050] Hereinafter, a treatment apparatus (anodizing apparatus) 1 that performs an anodizing process according to a second embodiment will be described referring to a FIGS. 3A-4B. The difference between the present embodiment and the first embodiment is the structure of the mount base 40. Therefore, members and mechanisms identical to those of the first embodiment are denoted by the same reference signs in FIGS. 3A-4B, and detailed description thereof will be omitted.

[0051] As shown in FIG. 3A, a mount base 40 includes a base body 45 that is conductive to the positive electrode of a power supply 14 and a frame 47 attached to the base body 45. The base body 45 is made of conductive material such as stainless steel. Therefore, unlike the mount base of the first embodiment, the base body 45 is not provided with a conducting member 30. Like the mount base of the first embodiment, the base body 45 includes a housing recess 40b for housing a substrate B. Further, as shown in FIGS. 4A and 4B, the base body 45 is provided with a suction passage 61 which is continuous with a space C formed between a side wall surface 41 of the housing recess 40b and a side surface Bs of the substrate B and sucks a fluid in the space C. A suction pump 63 is connected to the suction passage 61 via a suction pipe 62.

[0052] The frame 47 faces a peripheral region 13b of an electrolyte membrane 13. The frame 47 is made of insulating material such as resin or ceramics. As shown in FIG. 3A, the frame 47 includes an opening 47a. The treatment surface Ba of the substrate B is exposed from the opening 47a of the frame 47 while the substrate B is housed in the housing recess 40b of the base body 45. Therefore, the space region surrounded by the opening 47a of the frame 47 faces the contact region 13a of the electrolyte membrane 13, and the frame 47 faces the peripheral region 13b of the electrolyte membrane 13. The surface 40a of the mount base 40 facing the peripheral region 13b of the electrolyte membrane 13 is made of insulating material.

[0053] As shown in FIG. 3B, like the first embodiment, also in the present embodiment, the treatment surface Ba of the substrate B is first dried, and then the substrate B is placed on the mount base 40. At this time, the substrate B may be first housed in the housing recess 40b of the base body 45 and then the frame 47 may be attached. Next, a linear actuator 70 is moved to bring the contact region 13a of the electrolyte membrane 13 into contact with the treatment surface Ba of the substrate B. Next, a circulation pump 53 is driven to supply the electrolytic solution L to the container 15 and circulate the electrolytic solution L. In this state, voltage of the power supply 14 is applied between the substrate B and the cathode 11. At the same time, the suction pump 63 is actuated. Consequently, like the one shown in FIG. 2C, in the present embodiment in which an anodic oxide film Bf can be formed on a surface layer Bc including the treatment surface Ba of the substrate B, during the anodizing process, the surface 40a contacting the peripheral region 13b of the electrolyte membrane 13 is made of insulating material, and thus the same advantageous effect as the first embodiment can be expected.Example

[0054] An anodizing process was performed on the treatment surface Ba of the substrate B using the treatment apparatus shown in FIG. 1A. As the substrate B, 20 sheets of pure aluminum (A1050) were prepared. The size of the treatment surface Ba of the substrate B is 50 mm × 50 mm. The thickness of the substrate B is 0.5 mm. Next, as the electrolytic solution, 10% by weight of aqueous sulfuric acid solution was prepared. As the power supply, a DC power supply (model number ZX-400LA manufactured by Takasago Seisakusho Co., Ltd.) was used. As the cathode, a mesh electrode with an iridium-oxide-coating on the surface was prepared. The mesh diameter of the mesh electrode was 50 mm. 2L of the electrolytic solution was cooled on ice to below 10 °C. Then, voltage was applied between the substrate and the cathode under constant current conditions while circulating the electrolytic solution. The current conditions were a current-density of 1.0 A / dm2 and a current-density of 3 A / dm2. For each current condition, an anodic oxide film was formed for ten substrates.

[0055] FIG. 5A shows a result obtained in Example by measuring the relationship between a voltage application time and an applied voltage under treatment at a constant current (a current-density of 1A / dm2). As shown in FIG. 5A, when the application of the voltage started, the voltage value became higher due to a natural oxide film formed on the treatment surface of the substrate. However, as the application time goes by, the applied voltage stabilized to a substantially constant value (substantially 20 V). When a metal film is formed with the same constant current using the film forming apparatus shown in the background art, the applied voltage is about 5 V. Therefore, the applied voltage during the anodizing process is higher than the applied voltage during metal film formation. This is considered to be because an oxide film is formed on the treatment surface of the substrate when the anodizing process is performed.

[0056] FIG. 5B shows a result obtained in Example showing the relationship between a voltage application time and a film thickness under treatment at a constant current (a current-density of 1 A / dm2 and a current-density of 3 A / dm2). In FIG. 5B, a result obtained by forming an anodic oxide film on the substrate in a bath containing an electrolytic solution is shown by a solid line as a reference example. In view of this result, the result of a current-density of 1 A / dm2 was substantially the same as the result of the reference example. Furthermore, it was found that, when the applied voltage was constant, increasing the current density resulted in faster formation of the anodic oxide film up to a predetermined film thickness. This was because the surface of the mount base facing the peripheral region of the electrolyte membrane was made of insulating material, and thus it was possible to efficiently pass the current between the cathode and the substrate.

[0057] Furthermore, the treatment surface and the cross section of the substrate on which the anodizing process was performed under the condition of a current-density of 3 A / dm2 was observed. The results are shown in FIGS. 6A-6D. FIG. 6A is a photograph of the treatment surface of the substrate in Example. FIG. 6B is a photograph obtained by observing the treatment surface of the substrate of FIG. 6A with an electron microscope. FIG. 6C is a cross-sectional photograph of the substrate in Example. FIG. 6D is a photograph obtained by observing the cross section of the substrate of FIG. 6C with the electron microscope.

[0058] As can be seen in FIG. 6C, the surface layer including the treatment surface of the substrate is an alumite film (anodic oxide film). Further, as shown in FIGS. 6B and 6D, micropores unique to the alumite film were formed on the treatment surface of the substrate on which the anodizing process was performed.

[0059] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above-described embodiments, and various design changes can be made within the scope without departing from the spirit of the present disclosure described in the claims.

[0060] In the second embodiment, the frame made of insulating material was attached to the base body made of conductive material. However, for example, a surface of the base body that contacts the peripheral region of the electrolyte membrane may be coated with conductive material such as resin.

Examples

first embodiment

[0027]Hereinafter, a treatment apparatus (anodizing apparatus) 1 that performs an anodizing process according to a first embodiment will be described referring to FIGS. 1A-2C. In the present embodiment, the treatment apparatus 1 includes a cathode 11, an electrolyte membrane 13, and a power supply 14 that applies voltage between the cathode 11 and a substrate B.

[0028]As shown in FIGS. 1A and 2A, the treatment apparatus 1 further includes a container 15 that contains the cathode 11 and an electrolytic solution L and a mount base 40 on which the substrate B is placed. The treatment apparatus 1 further includes a linear actuator 70 for raising and lowering the container 15. The linear actuator 70 raises and lowers the container 15 by linearly moving a rod 72 to allow the electrolyte membrane 13 and the substrate B to come in contact with and separate from each other. The linear actuator 70 has the rod 72 that moves linearly with respect to a body 71. The container 15 is securely fixed ...

second embodiment

[0050]Hereinafter, a treatment apparatus (anodizing apparatus) 1 that performs an anodizing process according to a second embodiment will be described referring to a FIGS. 3A-4B. The difference between the present embodiment and the first embodiment is the structure of the mount base 40. Therefore, members and mechanisms identical to those of the first embodiment are denoted by the same reference signs in FIGS. 3A-4B, and detailed description thereof will be omitted.

[0051]As shown in FIG. 3A, a mount base 40 includes a base body 45 that is conductive to the positive electrode of a power supply 14 and a frame 47 attached to the base body 45. The base body 45 is made of conductive material such as stainless steel. Therefore, unlike the mount base of the first embodiment, the base body 45 is not provided with a conducting member 30. Like the mount base of the first embodiment, the base body 45 includes a housing recess 40b for housing a substrate B. Further, as shown in FIGS. 4A and 4B...

example

[0054]An anodizing process was performed on the treatment surface Ba of the substrate B using the treatment apparatus shown in FIG. 1A. As the substrate B, 20 sheets of pure aluminum (A1050) were prepared. The size of the treatment surface Ba of the substrate B is 50 mm × 50 mm. The thickness of the substrate B is 0.5 mm. Next, as the electrolytic solution, 10% by weight of aqueous sulfuric acid solution was prepared. As the power supply, a DC power supply (model number ZX-400LA manufactured by Takasago Seisakusho Co., Ltd.) was used. As the cathode, a mesh electrode with an iridium-oxide-coating on the surface was prepared. The mesh diameter of the mesh electrode was 50 mm. 2L of the electrolytic solution was cooled on ice to below 10 °C. Then, voltage was applied between the substrate and the cathode under constant current conditions while circulating the electrolytic solution. The current conditions were a current-density of 1.0 A / dm2 and a current-density of 3 A / dm2. For each cu...

Claims

1. An anodizing apparatus that applies voltage between an cathode and a substrate to perform an anodizing process on a treatment surface of the substrate, the anodizing apparatus comprising:a container having an opening at a position facing the substrate, the opening covered by an electrolyte membrane with an electrolytic solution contained in the container;a cathode disposed inside of the container at a position facing the electrolyte membrane;a power supply that applies voltage between the cathode and the substrate; anda mount base on which the substrate is placed, the mount base being disposed at a position facing the cathode with the electrolyte membrane interposed therebetween,wherein the electrolyte membrane has a contact region that contacts the treatment surface of the substrate and a peripheral region that faces the mount base so as to surround the contact region, andwherein, a surface of the mount base facing the peripheral region is made of insulating material.

2. The anodizing apparatus according to claim 1,wherein the mount base is made of the insulating material, andwherein a conducting member is embedded in the mount base, the conducting member allowing a contact surface of the substrate that contacts the mount base to be conductive to a positive electrode of the power supply.

3. The anodizing apparatus according to claim 2,wherein the mount base has a housing recess for housing the substrate while the substrate is placed thereon, andwherein the mount base is provided with a suction passage that is continuous with a space formed between a side wall surface of the housing recess and a side surface of the substrate and sucks a fluid in the space.

4. The anodizing apparatus according to claim 1, wherein the mount base includes a base body that is made of conductive material and is conductive to a positive electrode of the power supply, and a frame attached to the base body and made of the insulating material facing the peripheral region.

5. An anodizing method using the anodizing apparatus according to claim 1, the anodizing method comprising:first drying a treatment surface of the substrate, then placing the substrate on the mount base; andbringing the contact region of the electrolyte membrane into contact with the treatment surface of the substrate and applying voltage of the power supply between the substrate and the cathode to form an anodic oxide film on a surface layer including the treatment surface of the substrate.

Images