JP2023085311A - Aluminum member and production method thereof - Google Patents

Abstract

To provide an aluminum member for immunochromatography with high whiteness and water absorption performance, and a method for producing the same.SOLUTION: An aluminum member 100 includes a porous layer 40 containing a base material 11 composed of metallic aluminum and a film 12 containing aluminum oxide covering a surface of the base material 11. The film 12 has a thickness of 5 to 1,000 nm, the film 12 has a plurality of at least one of recesses 13 and/or convex parts formed on a surface, the recesses 13 are 10-100 nm in depth, and the convex parts are 10-100 nm in height. The porous layer 40 has a plurality of pores 15 with an average pore size of 0.1 to 10 μm.SELECTED DRAWING: Figure 2

Description

The present invention relates to an aluminum member and its manufacturing method.

Conventionally, a test kit using immunochromatography is known as an in-vitro diagnostic drug for quickly and simply testing for infection with, for example, influenza virus. For this test kit, for example, a sample collected from a living body is dropped onto a predetermined position, and if both the test line and the control line can be visually confirmed, the result is positive, and only the control line can be visually confirmed. It indicates that the test is negative.

A test kit, for example, as disclosed in Patent Document 1, includes a nitrocellulose membrane filter as a developing member for developing a specimen. The collected specimen flows through the membrane filter by capillary action and is developed to the test line and the control line.

Japanese Patent Application Laid-Open No. 2003-344406

Nitrocellulose membrane filters generally have a high degree of whiteness, making it relatively easy to visually confirm test lines and control lines, and are used in many test kits.

However, nitrocellulose membrane filters tend to have non-uniform pore sizes and thicknesses depending on production date, production location, production lot, and the like, resulting in large variations in quality. If there is such a large variation in quality, the flow velocity of the liquid flowing due to capillary action tends to be uneven, which may adversely affect the inspection results.

Nitrocellulose membrane filters generally do not have good storage stability. Therefore, there is a demand for a deployment member that can replace the nitrocellulose membrane filter with high whiteness and long shelf life.

The present invention has been made in view of the problems of the prior art. An object of the present invention is to provide an aluminum member having high whiteness and high water absorption performance, and a method for producing the same.

An aluminum member according to an aspect of the present invention includes a porous layer including a base material made of metal aluminum and a coating containing aluminum oxide covering the surface of the base material. The coating has a thickness of 5 nm to 1000 nm, and has at least one of a plurality of recesses and a plurality of protrusions formed on the surface. The depth of each recess included in the plurality of recesses is 10 nm to 100 nm, and the height of each protrusion included in the plurality of protrusions is 10 nm to 100 nm. The porous layer has a plurality of pores, and the average pore diameter of the plurality of pores is 0.1 μm to 10 μm.

A method for manufacturing an aluminum member according to an aspect of the present invention includes a film forming step of anodizing an aluminum plate having a porous structure to form a film containing aluminum oxide on the aluminum plate. A method for manufacturing an aluminum member includes a depolarization treatment step of depolarizing an aluminum plate having a film formed thereon and removing a part of the surface of the film. The film formation step and the depolarization treatment step are alternately repeated. The aluminum plate is made of metal aluminum.

FIG. 1 is a schematic cross-sectional view showing a tertiary roughened surface structure of a porous layer in which a part of the porous layer according to this embodiment is enlarged. FIG. 2 is a schematic cross-sectional view showing the primary rough surface structure and the secondary rough surface structure of the porous layer in which the portion surrounded by the frame in FIG. 1 is enlarged. FIG. 3 is a schematic cross-sectional view showing another example of the primary rough surface structure and the secondary rough surface structure of the porous layer. FIG. 4 is a schematic cross-sectional view showing another example of the primary rough surface structure and the secondary rough surface structure of the porous layer. FIG. 5 is a cross-sectional view showing an example of the aluminum member according to this embodiment. FIG. 6 is a perspective view showing an example of a test kit using an aluminum member according to this embodiment. FIG. 7 is a photograph of the surface of the etched aluminum plate observed with a scanning electron microscope (SEM). FIG. 8 is a photograph of the surface of the aluminum member according to Example 3 observed with a scanning electron microscope. FIG. 9 is a photograph of the surface of the aluminum member according to Example 10 observed with a scanning electron microscope. FIG. 10 is a photograph of the surface of the aluminum member according to Comparative Example 3 observed with a scanning electron microscope.

Hereinafter, an aluminum member according to the present embodiment and a method for manufacturing the same will be described in detail with reference to the drawings. The present invention is not limited only to the following embodiments. Also, some or all of the constituent elements in the embodiments can be combined as appropriate. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from the actual ratios.

[Aluminum member]
In this embodiment, it was investigated whether an aluminum member having a porous structure could be used as an alternative to the nitrocellulose membrane filter. However, it is generally considered difficult for an aluminum member to exhibit capillary action to the extent that it can be applied to immunochromatography. In addition, the aluminum member is usually gray, and it is difficult to confirm the coloring of the test line and the control line.

However, it was found that the aluminum member according to this embodiment, which will be described in detail below, has a high degree of whiteness and a high water absorption performance. Such an aluminum member is expected to be useful not only as a substitute for nitrocellulose membrane filters but also for various uses.

FIG. 1 is a schematic cross-sectional view enlarging a part of the porous layer 40 according to this embodiment. 2 to 4 are schematic cross-sectional views showing the primary rough surface structure 10 and the secondary rough surface structure 20 of the porous layer 40 in which the portion surrounded by the frame in FIG. 1 is enlarged. As shown in FIG. 1 , an aluminum member 100 according to this embodiment includes a porous layer 40 . Moreover, as shown in FIGS. 2 to 4, the porous layer 40 includes a base material 11 and a coating 12. As shown in FIG. In the porous layer 40 , the coating 12 is in contact with the base material 11 and the coating 12 is arranged on the outer surface side of the aluminum member 100 . The film 12 has at least one of concave portions 13 (first concave portions) and convex portions 14 (first convex portions) on its surface. Moreover, the porous layer 40 has a plurality of pores 15 .

<Rough surface structure>
The aluminum member 100 has a rough surface structure on its surface. A rough surface structure refers to a surface structure in which a surface is rougher than a smooth surface by having a plurality of unevenness on the surface. Preferably, the rough surface structure is one in which at least one of the concave portions 13 and the convex portions 14 is arranged dispersedly on the surface of the aluminum member 100 . It is preferable that the rough surface structure on the surface of the aluminum member 100 is not arranged with needle-like or plate-like uneven structures. The rough surface structure of the aluminum member 100 can be represented by a primary rough surface structure 10, a secondary rough surface structure 20, and a tertiary rough surface structure 30 in order of increasing scale of surface roughness. That is, the scale of the surface roughness of the secondary rough surface structure 20 is larger than the scale of the surface roughness of the primary rough surface structure 10 , and the scale of the surface roughness of the tertiary rough surface structure 30 is that of the secondary rough surface structure 20 . Greater than degree scale. As will be described later, it is presumed that the aluminum member 100 has the primary rough surface structure 10, the secondary rough surface structure 20, and the tertiary rough surface structure 30, thereby increasing the whiteness.

As shown in FIGS. 2 to 4, the primary rough surface structure 10 is a fine fine structure formed by the coating 12 and at least one of a plurality of concave portions 13 and a plurality of convex portions 14 existing on the surface of the coating 12. It has a rough surface structure. A primary rough surface structure 10 is formed on the surface of the coating 12 . The primary rough surface structure 10 is a structure whose surface roughness scale is on the order of several nanometers to several hundreds of nanometers.

As shown in FIGS. 2 to 4, the secondary rough surface structure 20 is a rough surface structure formed by the base material 11 and the plurality of pores 15 in the porous layer 40. FIG. That is, the secondary rough surface structure 20 is formed by a convex portion 21 (second convex portion, protruding portion) and a concave portion 22 (second concave portion, recessed portion). The convex portion 21 is formed by the base material 11 and the film 12 and protrudes outward from the porous layer 40 . The concave portion 22 is formed by the base material 11 and the film 12 and recesses toward the inside of the porous layer 40 . The pores 15 are formed by internal spaces of the porous layer 40 surrounded by the base material 11 forming the recesses 22 and the film 12 . In other words, the secondary rough surface structure 20 is formed on the surface of the aluminum member 100 by the base material 11 and the coating 12 itself. The secondary rough surface structure 20 is a structure whose surface roughness scale is on the order of several hundred nm to several tens of μm.

In this way, the porous layer 40 is a porous body having inside the pores 15 communicating with the outside. At this time, the pores 15 are surrounded by the film 12 . That is, while the concave portions 13 and convex portions 14 of the primary rough surface structure 10 are formed in the film 12 on the surface of the porous layer 40, the pores 15 of the secondary rough surface structure 20 are formed in the porous layer 40. It is formed surrounded by a base material 11 inside and a film 12 covering the surface thereof. The pores 15 forming one cell structure surrounded by the coating 12 may communicate with pores 15 forming another cell structure. Specifically, the porous layer 40 may be an open-cell structure. Also, the pores 15 may or may not penetrate from one surface of the porous layer 40 to the other surface.

As shown in FIG. 1 , the tertiary rough surface structure 30 is constituted by the outer surface of the porous layer 40 . The tertiary rough surface structure 30 is a coarse rough surface structure formed by gathering a plurality of irregularities due to the primary rough surface structure 10 and the secondary rough surface structure 20 . The tertiary rough surface structure 30 is an assembly formed by a set of the primary rough surface structure 10 and the secondary rough surface structure 20 on the surface of the aluminum member 100 . As will be described later, the tertiary rough surface structure 30 is formed by repeating the film forming step and the depolarization treatment step after the etching step, thereby forming an uneven structure composed of aggregates of the primary rough surface structure 10 and the secondary rough surface structure 20. Formed by development. The tertiary rough surface structure 30 is a structure whose surface roughness scale is on the order of several tens of μm to several hundred μm.

As shown in FIG. 1, a tertiary rough surface structure 30 composed of an assembly of a primary rough surface structure 10 and a secondary rough surface structure 20 forms an uneven structure on the surface of an aluminum member 100 . Specifically, the tertiary rough surface structure 30 is formed by an assembly of the primary rough surface structure 10 and the secondary rough surface structure 20, and the convex portions 31 (third convex portions, mountain portions) and concave portions 32 (third concave portions) , valleys) are formed. The convex portion 31 rises like a mountain in the thickness direction of the surface of the aluminum member 100 , and the concave portion 32 sinks like a valley in the thickness direction of the surface of the aluminum member 100 . These convex portions 31 and concave portions 32 appearing repeatedly at intervals, so that the tertiary rough surface structure 30 has a periodic ridge-and-valley structure with a larger scale than the primary rough surface structure 10 and the secondary rough surface structure 20. have.

The period of the tertiary rough surface structure 30 is preferably 10 μm to 500 μm, more preferably 30 μm to 200 μm. The period of the tertiary rough surface structure 30 means that the convex portions 31 that are adjacent to each other with the concave portion 32 interposed therebetween and periodically appear in the plane direction of the aluminum member 100, or the concave portions that are adjacent to each other with the convex portion 31 interposed and appear periodically. 32 intervals. By setting the period of the tertiary rough surface structure 30 within such a range, it is possible to provide the aluminum member 100 with better whiteness. The period of the tertiary rough surface structure 30 can be measured by observing the cross section of the aluminum member 100 with an optical microscope or the like.

Since the aluminum member 100 has the tertiary rough surface structure 30 as described above, the glossiness of the surface is reduced and the matte appearance is improved. As a result, gloss on the surface of the aluminum member 100 is suppressed, and the visibility of information such as colors, patterns, figures, symbols, and characters presented on the aluminum member 100 is improved. Such an improvement in visibility is effective, for example, when the aluminum member 100 is used as a test sheet or a development member for chromatography and the test results produced on the aluminum member 100 are visually or optically confirmed.

<Base material>
The base material 11 is made of metal aluminum. Metal aluminum constituting the base material 11 is preferably pure aluminum with a purity of 99% or more, more preferably pure aluminum with a purity of 99.9% or more, and pure aluminum with a purity of 99.98% or more. Aluminum is more preferred.

The base material 11 may contain inevitable impurities. In the present embodiment, unavoidable impurities mean those that are present in raw materials or that are unavoidably mixed in during the manufacturing process. The unavoidable impurities are essentially unnecessary impurities, but are allowable because they are in minute amounts and do not affect the properties of aluminum. Inevitable impurities that may be contained in aluminum are elements other than aluminum (Al). Examples of unavoidable impurities that may be contained in aluminum include magnesium (Mg), iron (Fe), silicon (Si), copper (Cu), lead (Pb), manganese (Mn), chromium (Cr ), zinc (Zn), titanium (Ti), gallium (Ga), boron (B), vanadium (V), zirconium (Zr), calcium (Ca), cobalt (Co), and the like. The total amount of unavoidable impurities in aluminum is preferably 1% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.02% by mass or less.

The shape of the base material 11 is not particularly limited, and may be porous, dendritic, fibrous, massive, spongy, or the like.

<Film>
The coating 12 covers the surface of the base material 11 . Specifically, the film 12 is in contact with the surface of the base material 11 and the pores 15, and suppresses the base material 11 from corroding.

Coating 12 contains aluminum oxide. In this embodiment, the film 12 is an anodized film, and the anodized film is preferably a barrier type anodized film. Moreover, the film 12 may contain aluminum hydroxide. Coating 12 may have a hydrated coating comprising aluminum hydroxide.

For example, the film 12 may be formed by laminating an anodized film and a hydrated film in this order from the base material 11 side. is preferably provided with a hydrated film. Alternatively, the film 12 may be a sea-island distribution of the anodized film and the hydrated film on the surface of the base material 11, but the anodized film is distributed like a sea on the surface of the base material 11. In addition, it is preferable that the hydrated film is distributed like islands. Specifically, the ratio of the hydrated film to the entire outer surface of the film 12 is preferably 5% or more and 50% or less, more preferably 10% or more and 40% or less, and 15% or more and 30% or less. is more preferable. In addition, when the film 12 contains aluminum hydroxide and the aluminum hydroxide is present on a part of the outermost surface of the base material 11 and the porous layer 40 , it is preferable that the aluminum hydroxide forms the protrusions 14 .

The porous layer 40 according to the present embodiment preferably does not include a hydrated film covering the base material 11 and the porous layer 40 over the entire outermost surface. Since the entire outermost surface of the porous layer 40 does not contain a hydrated film, diffuse reflection becomes dominant, and the whiteness of the aluminum member 100 can be further improved. Aluminum hydroxide is represented by the general formula Al(OH) ₃ .

When the outermost surface of the film 12 is covered with a needle-like or plate-like hydrated film, the aluminum member 100 may appear black or gray. This is because such a hydrated film has a sharp tip shape near the surface, and although this tip part contributes to the diffuse reflection of incident light, the part capable of diffuse reflection is the tip part. It is considered that the fact that the area is small is affected by the fact that it is limited to In addition, such a film has an internal shape in which the space between adjacent needle-like or plate-like hydrated films gradually narrows from the tip toward the root. Therefore, the incident light entering the inside is absorbed by the hydrated film while being repeatedly reflected, and the fact that the light is difficult to be emitted to the outside also affects the appearance of the aluminum member 100 in black or gray. it is conceivable that.

Furthermore, when the hydrated film exists, the primary rough surface structure 10 and the secondary rough surface structure 20 are often clogged, so the appearance of the aluminum member 100 tends to be black or gray. Therefore, it is preferable that the film 12 made of an anodized film is provided on the surface of the porous layer 40 and the concave portions 13 and the pores 15 are present on the outermost surface of the film 12 . On the other hand, aluminum hydroxide does not cover the entire outermost surface of the porous layer 40 to form a hydrated film, but is present in a granular or lumpy form on a part of the outermost surface of the porous layer 40 to form the protrusions 14. In this case, the convex portion 14 can improve the whiteness. Furthermore, the whiteness can be improved by the protrusions 14 and the recesses 13 exposed on the outermost surface of the porous layer 40 without being covered with the hydrated film. Further, when aluminum hydroxide covers the entire outermost surface of the porous layer 40 to form a hydrated film, and is present in the form of particles or lumps on the outermost surface of the porous layer 40 to form the protrusions 14, , the convex portion 14 can improve the whiteness.

Coating 12 typically has a thickness of 5 nm to 1000 nm. The thickness of the film 12 is preferably 20 nm to 800 nm, more preferably 30 nm to 500 nm, even more preferably 50 nm to 300 nm. By setting the thickness of the film 12 within such a range, it becomes easier to ensure a sufficient thickness for diffusely reflecting the light incident on the porous layer 40, and the aluminum member 100 with better whiteness is provided. can do. Furthermore, it is possible to provide the aluminum member 100 with sufficiently high corrosion resistance. The thickness of the coating 12 can be measured, for example, by observing the cross section of the coating 12 with a scanning electron microscope or the like. In this specification, the thickness of the film 12 means the thickness excluding the concave portions 13 and the convex portions 14 .

The coating 12 has at least one of a plurality of concave portions 13 and a plurality of convex portions 14 formed on the surface. Specifically, as shown in FIG. 2 , the coating 12 may have a plurality of recesses 13 on the surface of the coating 12 . Alternatively, as shown in FIG. 3 , the coating 12 may have a plurality of protrusions 14 on the surface of the coating 12 . Alternatively, as shown in FIG. 4 , the coating 12 may have concave portions 13 and convex portions 14 on the surface of the coating 12 . In other words, the film 12 may have either the concave portion 13 or the convex portion 14 or both the concave portion 13 and the convex portion 14 . The presence or absence of the concave portion 13 or the convex portion 14 can be determined by observing the surface of the film 12 with a scanning electron microscope or the like.

The concave portions 13 and the convex portions 14 contribute to the whiteness of the aluminum member 100 . The reason why the whiteness of the aluminum member 100 is improved by forming at least one of the concave portions 13 and the convex portions 14 on the surface of the film 12 is not necessarily clear, but is presumed as follows. First, when light is incident on the aluminum member, the incident light is reflected on the surface of the aluminum member. At this time, if the surface of the aluminum member is smooth, it exhibits a specular gloss. Here, when the surface of the aluminum member has fine unevenness, the incident light is diffusely reflected by the unevenness.

On the other hand, the aluminum member 100 according to the present embodiment can increase diffuse reflection on the surface of the film 12 by the concave portions 13 and the convex portions 14 . That is, when the film 12 has the concave portions 13, the concave portions 13 increase the area capable of diffusely reflecting the incident light, so the aluminum member 100 is observed to appear white. Similarly, when the film 12 has the projections 14, the area that can diffusely reflect the incident light is increased by the projections 14, so the aluminum member 100 is observed to appear white.

It is preferable that the concave portion 13 is recessed from the exposed surface of the film 12 toward the base material 11 . It is preferable that the bottom of the concave portion 13 does not penetrate to the base material 11 and that the film 12 is formed between the concave portion 13 and the base material 11 . Although the shape of the concave portion 13 is not particularly limited, it is preferably substantially U-shaped or substantially V-shaped in cross section in the lamination direction of the base material 11 and the film 12 (thickness direction of the film 12). As will be described later, the etched aluminum plate is anodized and depolarized to form a film 12 made of an anodized film on the surface of the base material 11 . Recesses 13 are formed in this anodized film. The protrusions 14 are preferably formed to project outward from the exposed surface of the film 12 . Although the shape of the projections 14 is not particularly limited, it is preferably granular or massive.

The diameter of each recess 13 included in the plurality of recesses is preferably 10 nm to 200 nm, more preferably 20 nm to 150 nm, even more preferably 50 nm to 100 nm. The diameter of each projection 14 included in the plurality of projections is preferably 10 nm to 200 nm, more preferably 20 nm to 150 nm, even more preferably 50 nm to 100 nm. By setting the diameters of the concave portions 13 and the convex portions 14 within such a range, the light incident on the porous layer 40 is easily diffusely reflected by the concave portions 13 and the convex portions 14, and the aluminum member 100 having a better whiteness can be obtained. can provide. The diameter of the concave portion 13 can be obtained by observing the surface of the film 12 with a scanning electron microscope or the like and measuring the diameter of the inlet portion of the concave portion 13 . The diameter of the projections 14 can be obtained by observing the surface of the film 12 with a scanning electron microscope or the like and measuring the diameter of the portion where the diameter of the projections 14 is the largest.

Here, certification of the recesses 13 and their diameters when a plurality of recesses 13 are close to each other will be described. First, the position of the recess 13 is determined by the deepest position (peak position on the bottom side) of the recess 13 . The interval between adjacent recesses 13 can be determined by the distance between the bottom-side peak positions of the respective recesses 13 . When a recess 13 exists with a distance of 50 nm or more from surrounding recesses 13, this recess 13 is regarded as an independent recess 13. FIG. On the other hand, when a plurality of recesses 13 are clustered at intervals of less than 50 nm and form a cluster that exists at intervals of 50 nm or more from the surrounding recesses 13 that are not included in the cluster. , this group is regarded as one recess 13 . Then, the diameter of the entire group is measured as the diameter of the concave portion 13 . In addition, when a plurality of recesses 13 share the periphery of the recesses and the peak positions on the bottom side of the plurality of recesses 13 are vacant by 50 nm or more, the plurality of recesses 13 are separated and independent. Recess 13 is considered. At this time, by performing Voronoi division with the peak positions on the bottom side of the plurality of recesses 13 as generating points for the recesses sharing the peripheral edge portion, the regions belonging to the respective recesses 13 can be demarcated. .

Similarly, identification of the protrusions 14 and their diameters when a plurality of protrusions 14 are close to each other will be described. First, the position of the projection 14 is determined by the highest position (peak position on the top side) of the projection 14 . The interval between adjacent protrusions 14 can be determined by the distance between the peak positions on the top side of each protrusion 14 . When a certain convex portion 14 exists with a gap of 50 nm or more from the surrounding convex portions 14, this convex portion 14 is regarded as an independent convex portion 14. FIG. On the other hand, a plurality of protrusions 14 are clusters that are gathered at intervals of less than 50 nm, and form clusters that are present at intervals of 50 nm or more from the surrounding protrusions 14 that are not included in the cluster. If so, this cluster is regarded as one protrusion 14 . Then, the diameter of the whole cluster is measured as the diameter of the convex portion 14 . In addition, when there are a plurality of protrusions 14 sharing the peripheral edge of the protrusion, and the peak positions on the top side of the plurality of protrusions 14 are vacant by 50 nm or more, the plurality of protrusions 14 are separated from each other. is regarded as an independent projection 14. At this time, a region belonging to each convex portion 14 is demarcated by performing Voronoi division with the peak positions on the top side of the plurality of convex portions 14 as generating points for the overhangs sharing the peripheral portion. can be done.

The depth of each recess 13 included in the plurality of recesses is generally 10 nm to 100 nm, preferably 20 nm to 80 nm, and 30 nm to 50 nm in a cross-sectional view in the lamination direction of the base material 11 and the coating 12. is more preferable. The depth of the concave portion 13 can be obtained by observing the cross section of the film 12 with a scanning electron microscope or the like and calculating the average value of the distances from the entrance portion of the concave portion 13 to the bottom.

The height of each protrusion 14 included in the plurality of protrusions is generally 10 nm to 100 nm, preferably 20 nm to 80 nm, and preferably 30 nm to 50 nm in a cross-sectional view in the stacking direction of the base material 11 and the coating 12. is more preferable. The height of the projections 14 is obtained by observing the cross section of the film 12 with a scanning electron microscope or the like and calculating the average value of the distances from the surface of the flat part of the film 12 to the top of the projections 14. be able to.

If the depth of the concave portion 13 and the height of the convex portion 14 exceed the lower limits of the above ranges, the area of the concave portion 13 and the convex portion 14 that can diffusely reflect incident light increases, and the diffuse reflection tends to increase. Further, when the depth of the concave portion 13 and the height of the convex portion 14 are below the upper limit of the above range, the concave portion 13 and the convex portion 14 become, for example, a needle-like or plate-like uneven structure, resulting in a decrease in diffuse reflection. can be suppressed. The decrease in diffuse reflection is considered to be due to the fact that the needle-like or plate-like concave-convex structure reduces the area where the incident light can be diffusely reflected and causes the incident light to be absorbed. Thus, when the depth of the concave portion 13 and the height of the convex portion 14 are within the above ranges, the aluminum member 100 tends to appear white.

The density of the concave portions 13 and the convex portions 14 in the coating 12 is preferably 3 pieces/μm ² to 500 pieces/μm ² , more preferably 5 pieces/μm ² to 200 pieces/μm ² , and 10 pieces/μm 2 . /μm ² to 100/μm ² are more preferable. By setting the density of the concave portions 13 and the convex portions 14 to such a range, the light incident on the porous layer 40 is easily diffusely reflected by the concave portions 13 and the convex portions 14, and the aluminum member 100 having a better whiteness can be obtained. can provide. The density of the concave portions 13 and the convex portions 14 can be obtained by counting the total number of the concave portions 13 and the convex portions 14 per unit area on the surface of the film 12 using a scanning electron microscope or the like.

The area ratio of the concave portions 13 and the convex portions 14 in the film 12 is preferably 5% to 80%, more preferably 20% to 70%, even more preferably 30% to 60%. By setting the area ratio of the concave portions 13 and the convex portions 14 to such a range, the light incident on the porous layer 40 is easily diffusely reflected by the concave portions 13 and the convex portions 14, and the aluminum member 100 having a better whiteness. can be provided. The area ratio of the concave portions 13 and the convex portions 14 represents the ratio of the area occupied by the concave portions 13 and the convex portions 14 to the surface area of the film 12 on the surface of the porous layer 40 in percentage. The area ratio of the concave portions 13 and the convex portions 14 can be obtained by calculating the total area occupied by the concave portions 13 and the convex portions 14 per unit area on the surface of the film 12 using a scanning electron microscope or the like.

The porous layer 40 has a plurality of pores, and the average pore diameter of the plurality of pores is 0.1 μm to 10 μm. The average pore size of the pores 15 in the porous layer 40 is preferably 0.5 μm to 8 μm, more preferably 1 μm to 5 μm. The average pore diameter d (μm) in the porous layer 40 is preferably within the range represented by the following formula, where t seconds is the time required for the aluminum member 100 to absorb 4 cm of water.
Average pore diameter d = k/t
Here, k is a constant, specifically k is preferably 200-2000, more preferably 500-1500. Such pores 15 make it easier to ensure an appropriate diameter for sucking up water by capillary action, and the water sucking performance of the aluminum member 100 can be improved. The average pore diameter of the pores 15 can be measured, for example, by mercury porosimetry. The diameter of the concave portion 13 or the convex portion 14 is preferably within the above-described predetermined range and smaller than the average pore size of the porous layer 40 . Specifically, the diameter of the concave portion 13 is preferably 10 nm to 200 nm and smaller than the average pore size of the porous layer 40 . The diameter of the projections 14 is preferably 10 nm to 200 nm and smaller than the average pore diameter of the porous layer 40 .

The thickness of the porous layer 40 is preferably 30 μm to 10 cm. By setting the thickness of the porous layer 40 to such a range, it becomes easy to secure a sufficient thickness for sucking up water by capillary action, and the aluminum member 100 with better whiteness and water sucking performance is provided. can do. The thickness of the porous layer 40 is preferably 40 μm or more, more preferably 50 μm or more. The thickness of the porous layer 40 is more preferably 1000 μm or less, even more preferably 200 μm or less, and particularly preferably 150 μm or less.

<Substrate>
As shown in FIG. 5, the aluminum member 100 may further include a substrate 50. As shown in FIG. The substrate 50 can support the porous layer 40 and improve the rigidity of the aluminum member 100 . The substrate 50 may have a layered shape.

The porous layer 40 may be provided on at least one side of the substrate 50 . Specifically, the porous layer 40 may be provided only on one surface side of the substrate 50 or may be provided on both surface sides of the substrate 50 . The porous layer 40 is preferably arranged on the outermost surface of the aluminum member 100 .

Since the aluminum member 100 does not necessarily have the substrate 50, the thickness of the substrate 50 is more than 0 μm. The thickness of the substrate 50 may be, for example, 1 mm or less, 100 μm or less, 10 μm or less, or 1 μm or less, depending on the application.

The material forming the substrate 50 may be substantially the same material as the base material 11 . When the substrate 50 and the base material 11 are made of the same material, the substrate 50 and the base material 11 may be integrally formed. In this case, the substrate 50 and the base material 11 of the porous layer 40 may be formed continuously. The substrate 50 may be made of metal aluminum. Metal aluminum constituting the substrate 50 is preferably pure aluminum with a purity of 99% or more, more preferably pure aluminum with a purity of 99.9% or more, and pure aluminum with a purity of 99.98% or more. is more preferable.

The thickness of the aluminum member 100 may be, for example, 50 μm or more, 100 μm or more, or 150 μm or more, depending on the application. Also, the thickness of the aluminum member 100 may be 300 μm or less, 250 μm or less, or 200 μm or less. By setting the thickness of the aluminum member 100 within such a range, it is possible to provide the aluminum member 100 with good bending strength.

The arithmetic mean roughness Sa of the aluminum member 100 is preferably 0.1 μm to 30 μm, more preferably 0.6 μm to 20 μm, even more preferably 1 μm to 10 μm. By setting the arithmetic mean roughness Sa within such a range, the L ^* value tends to increase, making it easier to provide the aluminum member 100 with better whiteness. The arithmetic mean roughness Sa can be obtained by measuring the surface of the aluminum member 100 on the porous layer 40 side according to ISO25178. In this specification, the arithmetic mean roughness Sa of the aluminum member 100 mainly reflects the roughness due to the secondary rough surface structure 20 .

The aluminum member 100 preferably has an L ^* value of 80 or more, more preferably 85 or more, even more preferably 90 or more, and 95 or more in the L ^* a ^* b ^* color system. is particularly preferred. The L ^* value in the L ^* a ^* b ^* color system can be obtained according to JIS Z8722:2009 (color measurement method-reflection and transmission object color). Specifically, the L ^* value can be measured using a colorimeter or the like, and can be measured under conditions such as a diffuse illumination vertical light receiving method (D/0), a viewing angle of 2°, and a C light source. .

The aluminum member 100 preferably has a water suction height of 3 cm or more, more preferably 4 cm or more, and even more preferably 5 cm or more due to capillary action. By doing so, for example, the aluminum member 100 suitable for chromatography can be provided. The suction height is, for example, the height at which water is sucked up by capillary action after the aluminum member 100 is immersed in pure water so that the planar direction of the aluminum member 100 is perpendicular to the liquid surface and left for 10 minutes. It can be obtained by measuring the thickness. The pure water is pure water having a specific resistance of 10 kΩm measured at 30°C.

It is preferable that the aluminum member 100 does not break even if it is bent 100 times or more in a bending test according to the MIT type bending test method. When the aluminum member 100 satisfies such requirements, storage and transport of the aluminum member 100 in a roll form are facilitated. The MIT type folding test method is specified in EIAJ RC-2364A, and the MIT type folding test device uses the device specified in JIS P8115 (Paper and paperboard-Folding strength test method-MIT tester method). can do.

As described above, the aluminum member 100 according to the present embodiment includes the porous layer 40 including the base material 11 made of metal aluminum and the coating 12 containing aluminum oxide covering the surface of the base material 11 . The coating 12 has a thickness of 5 nm to 1000 nm, and has at least one of a plurality of concave portions 13 and a plurality of convex portions 14 formed on the surface. The depth of each recess 13 included in the plurality of recesses 13 is 10 nm to 100 nm, and the height of each protrusion 14 included in the plurality of protrusions 14 is 10 nm to 100 nm. The porous layer 40 has a plurality of pores 15, and the average pore diameter of the plurality of pores 15 is 0.1 μm to 10 μm.

The aluminum member 100 may further include a substrate 50 made of metal aluminum, and the porous layer 40 may be provided on at least one surface of the substrate 50 .

The aluminum member 100 according to the present embodiment has high whiteness and water absorption performance, but is not limited to applications that require both of these properties, and is suitable for applications that require either one of these properties. can also be used.

Examples of useful applications of the aluminum member 100 according to the present embodiment include, for example, gas or liquid separation membranes; moisture absorbing materials; water absorbing materials; Absorption material; Wiping sheet; Test sheet for chemicals such as concentrated sulfuric acid, urinalysis and pH test; Development member for chromatography such as thin layer chromatography; Material for disinfection and sterilization; separators such as batteries and electric double layer capacitors; catalyst carriers; reaction sites such as synthesis reactions; heat insulating materials; Examples of the separation membrane include reverse osmosis membranes, ion exchange membranes and gas separation membranes. Examples of the adsorbent material include masks, filtration membranes, and filters.

Since the aluminum member 100 has a high degree of whiteness, it is preferably used as a test sheet, a development member for chromatography, a reflector, and a standard white plate. In addition, since the aluminum member 100 is porous, it is preferably used as a separation membrane, a moisture absorbing material, a water absorbing material, an adsorbing material, a developing member for chromatography, a separator, a catalyst carrier, a reaction field, and a heat insulating material.

Among these, the aluminum member 100 is more preferably used for chromatography because of its high whiteness and water absorption performance. Among chromatography, lateral flow chromatography is more preferable. Also, the chromatography is preferably immunochromatography. Among immunochromatographies, lateral flow immunoassays are more preferred. Therefore, the aluminum member 100 may be a development member for chromatography. The chromatography developing member may be a chromatography test strip. In addition, the aluminum member 100 is preferably used for in-vitro diagnostic medicines such as test kits using immunochromatography. Note that the test kit may also be referred to as a diagnostic kit.

[Test kit]
Next, an example of a test kit 200 using the aluminum member 100 will be described. As shown in FIG. 6, the test kit 200 includes an aluminum member 100. As shown in FIG. Specifically, the test kit 200 includes an aluminum member 100 , a specimen supply section 110 , a determination section 120 and an absorption section 130 .

The sample supply unit 110 may contain, for example, a labeled antibody that specifically binds to a detection target such as influenza virus. A sample collected from a living body or the like is supplied to the sample supply unit 110 and mixed with the labeled antibody to form a mixed solution. The mixed liquid is spread to the determination section 120 by capillary action of the aluminum member 100 , and excess specimen is absorbed by the absorption section 130 .

The determination section 120 has, for example, a test line and a control line. For example, an antibody that specifically binds to the detection target is immobilized on the test line. When the sample contains a target to be detected, the labeled antibody is immobilized on the antibody in the test line via the target to be detected. On the control line, for example, an antibody that specifically binds to the labeled antibody is immobilized. When the mixture containing the specimen and the labeled antibody is developed up to the control line, the labeled antibody binds to the antibody immobilized on the control line.

A labeled antibody generally includes a label such as colored particles or colloidal gold particles, and an antibody that binds to the label to form a complex and specifically binds to a detection target. Therefore, when there is a portion where the concentration or density of the labeled antibody is high, this portion can be visually confirmed because the labels are concentrated. Therefore, with the test kit 200, it is possible to test positive when both the test line and the control line can be visually confirmed, and negative when only the control line can be visually confirmed. .

The test kit 200 can be used, for example, for infectious disease testing; genetic analysis; pregnancy testing; livestock testing;

Objects to be tested by the test kit 200 include, for example, amino acids, peptides, proteins, genes, sugars, lipids, cells, or complexes thereof. More specifically, peptides such as PCT (procalcitonin); proteins such as urinary albumin; hormones such as HCG (human chorionic gonadotropin) and LH (luteinizing hormone); HBs antigen, rotavirus antigen, adenovirus antigen , RSV (Respiratory Syncytial virus) antigen, influenza virus antigen, norovirus antigen, mump virus antigen, cytomegalovirus antigen, herpes simplex virus antigen, varicella-zoster virus antigen, SARS (severe acute respiratory syndrome) antigen, HBs antibody, HCV Antigens or antibodies of viral infections such as (hepatitis C virus) antibody, HIV antibody, EBV antibody, RSV antibody, rubella virus antibody, measles virus antibody, enterovirus antibody, dengue virus antibody, SARS antibody; pneumococcal antigen, mycoplasma antigen, Group A Streptococcus hemolytic antigen, Legionella antigen, Mycobacterium tuberculosis antigen, Neisseria gonorrhoeae antigen, Tetanus antigen, Antigen or antibody of bacterial infection such as Mycoplasma antibody, Helicobacter pylori antibody, Tubercle bacillus antibody; Chlamydia infection antigen such as Chlamydia antigen antigens or antibodies; spirochete infection antigens or antibodies such as Treponema pallidum antibodies; protozoal disease antigens or antibodies such as malaria antibodies or Toxoplasma antibodies;

[Manufacturing method of aluminum member]
Next, a method for manufacturing the aluminum member 100 according to this embodiment will be described. The method for manufacturing the aluminum member 100 of the present embodiment is not particularly limited, but includes, for example, an etching process, a film forming process, and a depolarization process. Moreover, the manufacturing method of the aluminum member 100 may have a hydration treatment process as needed. Each step will be described in detail below.

(Etching process)
In the etching step, before the film forming step, the aluminum plate is etched to form a porous structure in the aluminum plate. The etching process can form an aluminum plate having a porous structure with a plurality of pits. In the etching step, the base material 11 is formed by etching the aluminum plate. The same material as the substrate 50 described above can be used for the aluminum plate. That is, the aluminum plate may be made of metal aluminum.

In the etching process, pits are formed in the aluminum plate to make the aluminum plate porous. Thereby, by making the aluminum plate into a porous body having a porous structure, the surface area can be increased. The etching process can be performed by, for example, electrolytic etching, chemical etching, or the like. Electrolytic etching includes DC electrolytic etching and AC electrolytic etching. Chemical etching includes chemical etching using an acid solution and chemical etching using an alkaline solution. These etching techniques may be performed singly or in combination.

Here, electrolytic etching will be described as an example. In the etching step, direct current electrolytic etching is performed to form pits on the surface of the aluminum plate. The pits grow in a tunnel shape in the depth direction, which is the direction perpendicular to the surface of the aluminum plate, and the diameter of the pits increases. Expanding. Also, by performing AC electrolytic etching, pits are formed in three-dimensional directions and grow like a sponge, and the diameter of the pits increases. When the pits grow to the center of the aluminum plate, the aluminum member 100 made of the porous layer 40 is formed. Also, when the pits do not grow to the central portion of the aluminum plate and the porous layer 40 is not formed in the central portion, the aluminum member 100 composed of the porous layer 40 and the substrate 50 is formed.

In this embodiment, the etching of the substrate 50 is preferably AC electrochemical etching. Although the etching conditions are not particularly limited, for example, the etching time is 1 minute to 60 minutes and the etching temperature is 20.degree. C. to 80.degree. In the case of electrochemical etching, for example, current densities are between 50 mA/cm ² and 500 mA/cm ² .

The etching solution used for etching is preferably an aqueous solution containing hydrochloric acid. The concentration of the hydrochloric acid aqueous solution is preferably 6% by mass to 25% by mass. The aqueous hydrochloric acid solution may contain aluminum ions derived from aluminum chloride or the like in order to suppress excessive dissolution of aluminum. The concentration of aluminum chloride is preferably 0.1% by mass to 10% by mass.

The etching process may be performed in a single step process, or may be performed in a multi-step process that is divided into different plural stages. For example, the etching process may have a plurality of etching processes with different chemical species contained in the etching solution, concentration of the etching solution, etching time, etching temperature, current density, and the like.

(Film formation process)
In the film forming step, an aluminum plate having a porous structure is anodized to form a film 12 containing aluminum oxide on the surface of the aluminum plate. In the film forming process, the film 12 is formed by anodization on the surface of the base material 11 that has been made porous by the etching process. At this time, in the aluminum plate, the film 12 is formed on the surface of the base material 11 exposed to the outside and the surface of the base material 11 forming the pits inside. In the film forming step, for example, an anode provided with the substrate 50 and a cathode provided with stainless steel (SUS) are immersed in an electrolytic solution and electrolytically treated.

The electrolytic solution used for film formation is not particularly limited. For example, aqueous solutions of boric acid, ammonium borate, phosphoric acid, pyrophosphoric acid, ammonium phosphate, ammonium adipate, sulfuric acid, or oxalic acid can be used. The conditions for film formation are not particularly limited, but the voltage is, for example, 5V to 500V. The film formation may be performed in a single step process, or may be performed in a plurality of different steps.

(Depolarization process)
In the depolarization treatment step, the aluminum plate on which the film 12 is formed is subjected to depolarization treatment to remove part of the surface of the film 12 . In the depolarization process, part of the coating 12 formed in the coating forming process is removed, and voids and cracks remaining in the coating 12 are exposed. In addition, in the depolarization treatment step, the surface of the coating 12 is roughened by removing (eroding) the coating 12 , so that the concave portions 13 can be formed on the surface of the coating 12 . The depolarization treatment is performed, for example, by immersing an aluminum plate, which is a member on which the film 12 is formed in the film forming process, in a depolarization treatment liquid.

The depolarizing solution is not particularly limited as long as it can remove (erode) the surface of the aluminum oxide film, but is selected from the group consisting of phosphoric acids, metal salts of phosphoric acids, tartaric acid, hydrochloric acid, and metal salts of hydrochloric acid. It is preferably a solution in which at least one of them is dissolved, or at least one of a sodium hydroxide solution and an aqueous ammonia solution. Phosphoric acids include, for example, orthophosphoric acid, phosphorous acid, hypophosphorous acid, and mixtures thereof. Metals that form metal salts include, for example, aluminum, sodium, magnesium, calcium, zinc, and the like.

When phosphoric acids and phosphoric acid metal salts are used as the depolarizing solution, the content of phosphoric acids and phosphoric acid metal salts is preferably, for example, 0.1 g/L to 50 g/L. The treatment temperature for the phosphoric acid treatment is preferably, for example, 50°C to 80°C. Moreover, the treatment time of the phosphoric acid treatment is preferably 1 minute to 60 minutes.

In the method for manufacturing the aluminum member 100 according to the present embodiment, at least one of the plurality of concave portions 13 and the plurality of convex portions 14 are formed on the surface of the film by the film forming step and the depolarization treatment step. That is, in the method for manufacturing the aluminum member 100 according to the present embodiment, the etching step, the film forming step, and the depolarization treatment step can be performed in this order at least once. The number of times each step is performed is not particularly limited, but it is preferable to alternately repeat the film formation step and the depolarization treatment step after the etching step. As a result, the erosion of the coating 12 and the repair of the eroded coating 12 are repeated, thereby forming a good porous layer 40 . At least one of the plurality of concave portions 13 and the plurality of convex portions 14 is preferably formed by alternately repeating the film forming step and the depolarization treatment step two or more times. The number of repetitions of the film formation step and the depolarization treatment step is not particularly limited, but may be, for example, 20 times or less, or 15 times or less. The number of repetitions of the film formation step and the depolarization treatment step is preferably 2 to 10 times, more preferably 3 to 8 times. More preferably, the number of repetitions of the film formation step and the depolarization treatment step is 5 or more. By repeating the film formation process and the depolarization treatment process, a plurality of recesses 13 can be formed in the film 12, so that the whiteness of the aluminum member 100 can be improved.

(Hydration treatment step)
The method for manufacturing the aluminum member 100 according to the present embodiment may include a hydration treatment step, but when the hydration treatment step is performed, a film formation step and a depolarization treatment step are performed thereafter. It is preferable to carry out repeatedly. The method for manufacturing the aluminum member 100 may further include a hydration treatment step of hydrating the aluminum plate to form a hydrated film on the aluminum plate having a porous structure before the film forming step. The hydration treatment step is generally a step of forming a hydrated film with aluminum hydroxide on the surface of metal aluminum after the etching step. This is a heat treatment step. When fine irregularities on the surface are covered with aluminum hydroxide, the diffuse reflection of light is inhibited, and the whiteness of the aluminum member may decrease. Furthermore, since the porous portion of the aluminum member is likely to be clogged with aluminum hydroxide, diffuse reflection of light is inhibited and the whiteness of the aluminum member is lowered.

By omitting the hydration treatment process, the whiteness of the aluminum member 100 can be further improved. Further, when a hydrated film is formed by the hydration treatment process, the hydrated film can be dissolved by further performing anodization and depolarization treatment. As a result, the hydrated film can be reduced or eliminated, and the protrusions 14 can be formed on the surface of the film 12 . The whiteness degree can be improved by the protrusions 14 . At this time, it is considered that the convex portion 14 can be formed by the remaining hydrated film or anodized film.

Specifically, by performing anodization and depolarization treatment, the hydrated film on the inner layer side is sequentially incorporated into the anodized film, and the surface of the base material 11 consists of the anodized film and the remainder of the hydrated film. A film 12 results. In other words, a layered structure is produced in which the base material 11, the anodized film, and the remainder of the hydrated film are laminated in this order. This layer structure is further subjected to an anodizing treatment and a depolarizing treatment to form convex portions 14 on the film 12 .

In addition, depending on the conditions of the anodizing treatment and the depolarization treatment, the film 12 can be formed with the concave portions 13 as well as the convex portions 14 . Further, by performing the anodizing treatment and the depolarization treatment to such an extent that no hydrated film remains, the concave portions 13 can be formed on the surface of the film 12 . The convex portion 14 is formed by (the remainder of) the hydrated film or the anodized film.

As described above, pores 15 are generated in the porous layer 40 through the formation of pits in the base material 11 in the etching process to make the base material 11 porous, and the formation and removal of the anodized film in the film formation process and the depolarization treatment process. A secondary rough surface structure 20 is thereby formed. In addition, recesses 13 are formed on the surface of the coating 12 by the coating forming step and the depolarization treatment step, and the primary rough surface structure 10 is formed. In addition, by the film formation step and the depolarization treatment step after the hydration treatment step, convex portions 14 are generated on the surface of the film 12 to form the primary rough surface structure 10 . Further, after the etching step, by repeating the film formation step and the depolarization treatment step, an uneven structure composed of aggregates of the primary rough surface structure 10 and the secondary rough surface structure 20 develops, and the tertiary rough surface structure 30 is formed. be.

As described above, the method for manufacturing the aluminum member 100 has a film forming step of anodizing an aluminum plate having a porous structure to form the film 12 containing aluminum oxide on the aluminum plate. The method for manufacturing the aluminum member 100 includes a depolarization treatment step of depolarizing the aluminum plate on which the film 12 is formed and partially removing the surface of the film 12 . The film formation step and the depolarization treatment step are alternately repeated. The aluminum plate is made of metal aluminum. Furthermore, in the method for manufacturing the aluminum member 100, at least one of the plurality of concave portions 13 and the plurality of convex portions 14 are formed on the surface of the coating 12 by the coating forming step and the depolarization treatment step. Also, the film 12 has a thickness of 5 nm to 1000 nm. The depth of each recess 13 included in the plurality of recesses 13 is 10 nm to 100 nm, and the height of each protrusion 14 included in the plurality of protrusions 14 is 10 nm to 100 nm. The aluminum member 100 has a plurality of pores 15, and the average pore diameter of the plurality of pores 15 is 0.1 μm to 10 μm.

In this embodiment, the method for manufacturing the aluminum member 100 having the porous layer 40 by electrochemical etching or the like has been described. However, the method for manufacturing the aluminum member 100 is not limited to the above embodiment, and for example, the porous layer 40 may be formed by sintering aluminum powder.

EXAMPLES Hereinafter, the present embodiment will be described in more detail with reference to Examples and Comparative Examples, but the present embodiment is not limited to these.

[Example 1]
An aluminum foil having a thickness of 150 μm was subjected to AC electrolytic etching in an aqueous solution containing 3 mol/L hydrochloric acid and 0.2 mol/L sulfuric acid to make the surface of the aluminum foil porous, and then sufficiently washed with water. washed. High-purity aluminum with a purity of 99.98% was used as the aluminum foil.

FIG. 7 is a photograph showing how the surface of the aluminum plate after etching was observed with a scanning electron microscope. As shown in FIG. 7, the etched aluminum plate has a porous structure with a diameter of about 0.1 μm to 1 μm and a plurality of pits extending inside. A plurality of pits having a diameter of about 0.1 μm to 1 μm are formed on the surface of the aluminum plate and exposed to the outside, and the aluminum plate is roughened.

Next, the electrolytically etched aluminum foil was anodized to form a film on the surface of the base material made of pure aluminum. Specifically, the aluminum foil placed on the anode and the stainless steel (SUS) placed on the cathode were immersed in a boric acid electrolyte with a concentration of 80 g/L and a temperature of 70°C. . Then, it was anodized for 10 minutes at a voltage of 200V.

Next, after thoroughly washing the aluminum foil with the film formed thereon with water, it was immersed in a phosphoric acid aqueous solution having a concentration of 50 g/L and a temperature of 60° C. for 20 minutes for depolarization treatment.

Then, the anodizing and the depolarizing treatments were repeated in this order five times under the same conditions as above to fabricate an aluminum member.

[Example 2]
An aluminum member was produced in the same manner as in Example 1, except that the boric acid electrolyte used in the anodizing treatment was changed to a 1 g/L aqueous solution of ammonium dihydrogen phosphate and the anodizing treatment voltage was changed to 50V.

[Example 3]
An aluminum member was produced in the same manner as in Example 1, except that the boric acid electrolyte used in the anodizing treatment was changed to an ammonium adipate 100 g/L aqueous solution and the anodizing treatment voltage was changed to 150V.

[Example 4]
An aluminum member was produced in the same manner as in Example 1, except that the boric acid electrolyte used for the anodizing treatment was changed to a 50 g/L aqueous solution of oxalic acid, the anodizing treatment temperature was changed to 30 ° C., and the anodizing treatment voltage was changed to 20 V. made.

[Example 5]
Before the anodizing treatment, depolarization treatment was performed by immersing it in a phosphoric acid aqueous solution having a concentration of 50 g / L and a temperature of 60 ° C. for 10 minutes as a pretreatment, and the voltage of the anodizing treatment was changed to 150 V. , an aluminum member was produced in the same manner as in Example 1.

[Example 6]
An aluminum member was produced in the same manner as in Example 1, except that a hydrophilic coating agent was applied as post-treatment to the sample after repeated depolarization treatments.

[Example 7]
An aluminum member was produced in the same manner as in Example 1, except that one surface of the sample after repeated depolarization treatments was coated with a nylon resin having a thickness of 20 μm as a post-treatment.

[Example 8]
An aluminum member was produced in the same manner as in Example 1, except that one of the depolarization treatments with a phosphoric acid aqueous solution was changed to a heat treatment. The heat treatment was performed in air at 500° C. for 5 minutes.

[Example 9]
An aluminum member was produced in the same manner as in Example 1, except that the phosphoric acid aqueous solution used for the depolarization treatment was changed to a sodium hydroxide 5 g/L aqueous solution, and the depolarization treatment temperature was changed to 40°C.

[Example 10]
Before the anodizing treatment, the electrolytically etched aluminum foil was immersed in boiling pure water for 10 minutes for hydration treatment, and then anodizing treatment and depolarizing treatment were performed. Changed the number of repetitions to 7. An aluminum member was produced in the same manner as in Example 1 except for the above.

[Comparative Example 1]
An aluminum member was produced in the same manner as in Example 1, except that the electrolytically etched aluminum foil was anodized only once and was not depolarized.

[Comparative Example 2]
An aluminum member was produced in the same manner as in Example 1, except that the anodizing treatment and the depolarizing treatment were performed without performing electrolytic etching.

[Comparative Example 3]
An aluminum member was produced in the same manner as in Example 10, except that the number of repetitions of the anodizing treatment and the depolarizing treatment was changed to one.

[evaluation]
The surfaces of the aluminum members according to Examples 3, 10 and Comparative Example 3 were observed with a scanning electron microscope. Electron micrographs are shown in FIGS. 8, 9 and 10, respectively.

In the aluminum member obtained in each example, the film thickness, the diameter of the concave or convex portion of the primary structure, the depth of the concave portion or the height of the convex portion, the average pore diameter of the pores, the bending test, the arithmetic mean roughness Sa , the period of the tertiary rough surface structure, the L ^* value, and the water uptake height were evaluated as follows.

(Coating thickness)
After cutting the aluminum member, the cross-section polisher (registered trademark) manufactured by JEOL Ltd. was used to mirror-finish the cut surface to obtain a sample for coating thickness measurement. The cross-section of the film thickness measurement sample was observed with a scanning electron microscope ULTRA plus manufactured by Carl Zeiss Co., Ltd. to measure the thickness of the film.

(Diameter of concave portion of primary structure)
The surface of the film was observed with a scanning electron microscope ULTRA plus manufactured by Carl Zeiss Co., Ltd., and the diameter of the recesses was obtained by averaging the diameters of the entrance portions of the recesses.

(Diameter of convex portion of primary structure)
The surface of the film was observed with a scanning electron microscope ULTRA plus manufactured by Carl Zeiss Co., Ltd., and the diameter of the convex portions was obtained by averaging the diameters of the portions where the convex portions were the largest.

(depth of recess)
The cross section of the film was observed with a scanning electron microscope, and the depth of the recesses was obtained by calculating the average value of the distances from the entrances of the recesses to the bottoms.

(Height of convex part)
The cross section of the film was observed with a scanning electron microscope, and the height of the projections was obtained by calculating the average value of the distances from the surface of the flat part of the film to the top of the projections.

(Average pore diameter of pores)
The average pore diameter of the pores was measured by mercury porosimetry.

(Bending test)
The bending test was performed according to the MIT-type bending test method (EIAJ RC-2364A) specified by the Japan Electronics Manufacturers Association. As the MIT-type folding tester, a device specified in JIS P8115 (Paper and cardboard-Folding endurance test method-MIT tester method) was used. In the bending test, the process of bending the aluminum member 90° and returning it to its original shape was regarded as one bending number, and the aluminum member was bent 100 times. was evaluated as “no”.

(Arithmetic mean roughness Sa)
The arithmetic mean roughness Sa of the porous layer side surface of the aluminum member was measured according to ISO25178. The measurement conditions for the arithmetic mean roughness Sa are as follows.

Measurement conditions for arithmetic mean roughness Sa Apparatus: Bruker AXS Co., Ltd. 3D white interference microscope Contour GT-I
Measurement range: 60 μm×79 μm
Objective lens: 115x Internal lens: 1x

(Period of tertiary rough surface structure)
The cross section of the obtained aluminum member was observed with an optical microscope to measure the period of the tertiary rough surface structure.

(L ^* value)
Based on JIS Z8722, the surface of the aluminum member was measured with a colorimeter to obtain the L ^* value. The colorimetric conditions are as follows.

Measurement conditions for L ^* value Color difference meter: CR400 manufactured by Konica Minolta Japan Co., Ltd.
Illumination/light-receiving optical system: Diffuse illumination vertical light-receiving system (D/0)
Observation condition: CIE 2° visual field color matching function approximation Light source: C light source Color system: L ^* a ^* b ^*

(water suction height)
The aluminum member was immersed in pure water so that the planar direction of the aluminum member was perpendicular to the liquid surface, and after standing for 10 minutes, the height at which water was sucked up by capillary action was defined as the water uptake height.

8, 9 and 10 are photographs of the surfaces of the aluminum members according to Example 3, Example 10 and Comparative Example 3, respectively, observed with a scanning electron microscope. The aluminum member according to Example 3 does not contain a hydrated film because it is not hydrated, and has a primary rough surface structure with concave portions having a diameter of 10 nm to 200 nm on the surface of the aluminum member, as indicated by the arrows. was formed. In the aluminum member according to Example 10, after forming a hydrated film by boiling with boiling pure water, anodizing treatment and depolarizing treatment were repeatedly performed. Therefore, as indicated by arrows, a primary rough surface structure was formed on the surface of the aluminum member by convex portions having a diameter of 10 nm to 200 nm. It is presumed that these recesses and protrusions contribute to the whiteness of the aluminum member. On the other hand, in the aluminum member of Comparative Example 3, since the anodizing treatment and the depolarizing treatment after the hydration treatment were insufficient, concave portions or convex portions were not formed, and a porous aluminum plate was obtained. The surface was covered with aluminum hydroxide having a needle-like or plate-like structure. Therefore, in Comparative Example 3, it is presumed that the whiteness of the aluminum member is lowered.

Next, Table 1 shows the evaluation results of the aluminum members obtained in each example.

As shown in Table 1, the aluminum members of Examples 1 to 10 were superior to the aluminum members of Comparative Examples 1 to 3 in whiteness (L ^* value) and water absorption performance. On the other hand, in Comparative Example 1, since the depolarization treatment was not performed after the anodizing treatment, no depressions or projections were formed, and the whiteness was low. Further, in Comparative Example 2, since electrolytic etching was not performed, pores were not formed, and the water absorption performance was insufficient. In Comparative Example 3, since the number of repetitions of the anodizing treatment and the depolarizing treatment after the hydration treatment was small, the entire surface was covered with a hydrated film and the whiteness was low.

The aluminum plate before etching (not shown) had an arithmetic mean roughness Sa of 0.37 μm and an L ^* value of 49.5. The arithmetic mean roughness Sa of the aluminum plate after etching shown in FIG. 7 was 0.336 μm, and the L ^* value was 71.4. Therefore, simply etching the aluminum plate does not increase the whiteness of the aluminum plate.

The entire contents of Japanese Patent Application No. 2018-174947 (filing date: September 19, 2018) are incorporated herein.

As described above, the present embodiment has been described with examples and comparative examples, but the present embodiment is not limited to these, and various modifications are possible within the scope of the gist of the present embodiment.

ADVANTAGE OF THE INVENTION According to this invention, the aluminum member with high whiteness and water absorption performance, and its manufacturing method can be provided.

REFERENCE SIGNS LIST 10 primary rough surface structure 11 base material 12 film 13 concave portion 14 convex portion 15 pore 20 secondary rough surface structure 30 tertiary rough surface structure 40 porous layer 50 substrate 100 aluminum member

An aluminum member for immunochromatography according to an aspect of the present invention includes a porous layer containing a base material made of metal aluminum and a coating containing aluminum oxide covering the surface of the base material. The coating has a thickness of 5 nm to 1000 nm, and has at least one of a plurality of recesses and a plurality of protrusions formed on the surface. The depth of each recess included in the plurality of recesses is 10 nm to 100 nm, and the height of each protrusion included in the plurality of protrusions is 10 nm to 100 nm. The porous layer has a plurality of pores, and the average pore diameter of the plurality of pores is 0.1 μm to 10 μm.
The diameter of each recess is 10 nm to 200 nm, and may be smaller than the average pore diameter of the porous layer.
The diameter of each projection may be 10 nm to 200 nm.
The aluminum member for immunochromatography has a primary rough surface structure formed by a coating, at least one of a plurality of concave portions and a plurality of convex portions, and a secondary rough surface structure formed by a base material and a plurality of pores. It may have a surface structure and a tertiary rough surface structure consisting of a set of a primary rough surface structure and a secondary rough surface structure.
The aluminum member for immunochromatography may have an arithmetic mean roughness Sa of 0.1 μm to 30 μm.
The aluminum member for immunochromatography may have an L ^* value of 80 or more in the L ^* a ^* b ^* color system .
The aluminum member for immunochromatography may have a water uptake height of 3 cm or more due to capillary action.
The aluminum member for immunochromatography does not need to be broken even after being bent 100 times or more in the bending test according to the MIT type bending test method.
The aluminum member for immunochromatography may further include a substrate made of metal aluminum, and a porous layer may be provided on at least one side of the substrate.

A method for producing an aluminum member for immunochromatography according to an aspect of the present invention comprises a film forming step of anodizing an aluminum plate having a porous structure to form a film containing aluminum oxide on the aluminum plate. A method for producing an aluminum member for immunochromatography includes a depolarization treatment step of depolarizing an aluminum plate having a film formed thereon and removing a portion of the surface of the film. The film formation step and the depolarization treatment step are alternately repeated. The aluminum plate is made of metal aluminum. At least one of a plurality of concave portions and a plurality of convex portions is formed on the surface of the film by the film forming step and the depolarization treatment step. The coating has a thickness of 5 nm to 1000 nm. Each recess included in the plurality of recesses has a depth of 10 nm to 100 nm. The height of each protrusion included in the plurality of protrusions is 10 nm to 100 nm. The aluminum member for immunochromatography has a plurality of pores, and the average pore diameter of the plurality of pores is 0.1 μm to 10 μm.
The method for producing an aluminum member for immunochromatography may further include an etching step of etching the aluminum plate to form a porous structure in the aluminum plate before the film forming step.
The method for producing an aluminum member for immunochromatography further includes a hydration treatment step of hydrating the aluminum plate to form a hydrated film on the aluminum plate having a porous structure before the film forming step. good too.
At least one of a plurality of concave portions and a plurality of convex portions is formed on the surface of the film by the film forming step and the depolarization treatment step, and at least one of the plurality of concave portions and the plurality of convex portions are formed in the film forming step. and the depolarization step may be alternately repeated two or more times.
At least one of the plurality of concave portions and the plurality of convex portions may be formed by alternately repeating the film formation step and the depolarization treatment step five times or more.
When the film formation step and the depolarization treatment step are alternately repeated, the treatment time for one depolarization treatment in the depolarization treatment step may be 20 to 60 minutes.

Claims (15)

A porous layer containing a base material made of metal aluminum and a coating containing aluminum oxide covering the surface of the base material,
the coating has a thickness of 5 nm to 1000 nm;
The coating has at least one of a plurality of concave portions and a plurality of convex portions formed on the surface,
Each recess included in the plurality of recesses has a depth of 10 nm to 100 nm,
The height of each protrusion included in the plurality of protrusions is 10 nm to 100 nm,
The aluminum member, wherein the porous layer has a plurality of pores, and the average pore diameter of the plurality of pores is 0.1 μm to 10 μm. 2. The aluminum member according to claim 1, wherein each recess has a diameter of 10 nm to 200 nm and is smaller than the average pore diameter of the porous layer. 3. The aluminum member according to claim 1, wherein each projection has a diameter of 10 nm to 200 nm. a primary rough surface structure formed by the coating and at least one of the plurality of concave portions and the plurality of convex portions;
a secondary rough surface structure formed by the base material and the plurality of pores;
a tertiary rough surface structure consisting of an assembly of the primary rough surface structure and the secondary rough surface structure;
The aluminum member according to any one of claims 1 to 3, having The aluminum member according to any one of claims 1 to 4, wherein the arithmetic mean roughness Sa is 0.1 µm to 30 µm. The aluminum member according to any one of claims 1 to 5, wherein the L ^* value in the L ^* a ^* b ^* color system is 80 or more. 7. The aluminum member according to any one of claims 1 to 6, wherein the water uptake height due to capillary action is 3 cm or more. The aluminum member according to any one of claims 1 to 7, which does not break even when it is bent 100 times or more in a bending test according to the MIT type bending test method. further comprising a substrate made of metal aluminum,
The aluminum member according to any one of claims 1 to 8, wherein the porous layer is provided on at least one side of the substrate. The aluminum member according to any one of claims 1 to 9, which is used for chromatography. a film forming step of anodizing an aluminum plate having a porous structure to form a film containing aluminum oxide on the aluminum plate;
A depolarization treatment step of depolarizing the aluminum plate on which the film is formed and removing a part of the surface of the film,
Alternately repeating the film forming step and the depolarizing treatment step,
The method for manufacturing an aluminum member, wherein the aluminum plate is made of metal aluminum. forming at least one of a plurality of concave portions and a plurality of convex portions on the surface of the coating by the coating forming step and the depolarization treatment step;
the coating has a thickness of 5 nm to 1000 nm;
Each recess included in the plurality of recesses has a depth of 10 nm to 100 nm,
The height of each protrusion included in the plurality of protrusions is 10 nm to 100 nm,
12. The method for manufacturing an aluminum member according to claim 11, wherein said aluminum member has a plurality of pores, and said plurality of pores have an average pore size of 0.1 μm to 10 μm. 13. The method for manufacturing an aluminum member according to claim 11, further comprising an etching step of etching said aluminum plate to form said porous structure in said aluminum plate before said film forming step. 14. The method according to any one of claims 11 to 13, further comprising a hydration treatment step of hydrating the aluminum plate and forming a hydrated film on the aluminum plate having the porous structure before the film forming step. The method for manufacturing the aluminum member according to 1. forming at least one of a plurality of concave portions and a plurality of convex portions on the surface of the coating by the coating forming step and the depolarization treatment step;
At least one of the plurality of concave portions and the plurality of convex portions is formed by alternately repeating the film forming step and the depolarization treatment step two or more times, any one of claims 11 to 14. 10. A method for manufacturing the aluminum member according to claim 1.

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